Proteopedia - User contributions [en]

Sandbox Reserved 460

2012-05-02T17:51:19Z

Erika England:

{{Sandbox_Reserved_Robert_B_Rose_1}}


<Structure load='3VKP' size='500' frame='true' align='right' caption='Nitrite Reductase' scene='Insert optional scene name here' />

=Nitrite Reductase=
=='''General Information'''==
Nitrogen is an essential element for plant growth and development. Many plants form symbiotic relationships with bacteria and fungi to fix elemental nitrogen from the atmosphere to a deliverable form for the plants to use. Other plants have enzymes that can reduce nitrates in the soil to ammonium in a two step reduction process involving nitrate reductase and nitrite reductase. Without a functional nitrite reductase, the plants accumulate excess nitrites in the cells which are toxic to plants.
=='''Overview'''==

Nitrite reductase is an enzyme that belongs to the Oxidoreductase family for catalyzing the six-electron reduction of nitrite into ammonia, using the reduced ferredoxin as the electron donor. It is a monomeric protein with molecular mass near 63 kDa characterized by a unique <scene name='Sandbox_Reserved_460/Active_site/3'>active site</scene> which contains a single [4Fe–4S] cluster and a single siroheme via a bridging sulfur atom from a cysteine residue. The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

Nitrite reductase is found in several organisms and different forms that reduce nitrite to various products. The enzyme displayed contains a siroheme and iron-sulfur cluster to reduce nitrite to ammonia in certain plants. It is found in the stromal space of chloroplasts. Several other types of iron-based enzymes in bacteria reduce nitrite to nitrous oxide. There are also several types of Copper Nitrite Reductases found in many different plants and bacteria.

=='''Mechanism'''==

The electron flow proceeds initially from reduced ferredoxin to the enzyme's [4Fe–4S] cluster and subsequently from the reduced cluster to the siroheme. Since ferredoxin is a one-electron donor, the enzyme must accumulate six electrons in one-electron steps before it can reduce nitrite. Eight protons are also required in the reduction reaction. Reduced ferredoxin binds to the enzyme near the iron-sulfur cluster which becomes reduced. The cluster then transfers an electron to the siroheme. The reduced siroheme binds nitrite. Five more electrons are transferred to siroheme in this way until nitrite is fully reduced.

:::::::::::NO2- + 6Fd(red) + 8H+ → NH3 + 6Fd(ox) + 2H2O

::[[Image:Pathway.jpeg]]

=='''Structure'''==

===Secondary Structures===
Nitrite Reductase has only one chain consisting of 591 residues. There are 27 <scene name='Sandbox_Reserved_460/Helices/1'>helices</scene> (35% of chain) and 25 <scene name='Sandbox_Reserved_460/Beta_sheets/1'>beta strands</scene> (20% of chain). The enzyme is composed of three alpha/beta <scene name='Sandbox_Reserved_460/3domains/1'>domains</scene> which are not as well classified as nitrate reductase.

===Ligands===
<scene name='Sandbox_Reserved_460/Siroheme/1'>Siroheme</scene> is an iron-containing, modified tetrapyrrole similar in structure to both a heme and chlorophyll. It is a heme-like prosthetic group used by nitrite reductase to carry out the six-electron reduction of nitrogen. Nitrite is reduced to ammonia while still bound to siroheme.
The siroheme-iron sulfur cofactor is at the interface of the three domains of the enzyme. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

The <scene name='Sandbox_Reserved_460/Fe-s_cluster/1'>iron-sulfer cluster</scene> is a prosthetic group involved in single electron transfer from reduced ferrodoxin to siroheme.

===Ligand Binding to Active Sites===
* <scene name='Sandbox_Reserved_460/Ac1/3'>AC1</scene> binds Siroheme
* <scene name='Sandbox_Reserved_460/Ac2/3'>AC2</scene> binds Iron-Sulfur Complex
* <scene name='Sandbox_Reserved_460/Ac3/2'>AC3</scene> binds Potassium ion
* <scene name='Sandbox_Reserved_460/Ac4/2'>AC4</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac5/2'>AC5</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac6/2'>AC6</scene> binds Nitrite

===Hydrophobic and Hydrophilic residues===
The enzyme contains <scene name='Sandbox_Reserved_460/Hydrophobic/2'>279 hydrophobic (in gray) and 274 hydrophilic (purple)</scene> amino acid residues.

=='''References'''==
#Crawford NM: Nitrate: Nutrient and Signal for Plant Growth. The Plant Cell 1995, 7:859-868.
#Schottler MA, Albus CA, Bock R: Photosystem I: Its biogenesis and function in higher plants. Journal of Plant Physiology 2011, 168:1452-1461.
#Vincentz M, Moureaux T, Leydecker MT, Vaucheret H, Caboche M: Regulation of nitrate and nitrite reductase expression in Nicotiana plumbaginifolia leaves by nitrogen and carbon metabolites. The Plant Journal 1993, 3:315-324.
#Campbell WH, Kinghorn Jr: Functional domains of assimilatory nitrate reductases and nitrite reductases. Trends in Biochemical Sciences 1990, 15:315-319.
#Hirasawa M, Knaff DB: Interaction of ferredoxin-linked nitrite reductase with ferredoxin. BBA Protein Structure and Molecular Enzymology 1985, 830:173-180.

Sandbox Reserved 460

2012-05-02T17:15:55Z

Erika England:

{{Sandbox_Reserved_Robert_B_Rose_1}}


<Structure load='3VKP' size='500' frame='true' align='right' caption='Nitrite Reductase' scene='Insert optional scene name here' />

=Nitrite Reductase=
=='''General Information'''==
Nitrogen is an essential element for plant growth and development. Many plants form symbiotic relationships with bacteria and fungi to fix elemental nitrogen from the atmosphere to a deliverable form for the plants to use. Other plants have enzymes that can reduce nitrates in the soil to ammonium in a two step reduction process involving nitrate reductase and nitrite reductase. Without a functional nitrite reductase, the plants accumulate excess nitrites in the cells which are toxic to plants.
=='''Overview'''==

Nitrite reductase is an enzyme that belongs to the Oxidoreductase family for catalyzing the six-electron reduction of nitrite into ammonia, using the reduced ferredoxin as the electron donor. It is a monomeric protein with molecular mass near 63 kDa characterized by a unique <scene name='Sandbox_Reserved_460/Active_site/3'>active site</scene> which contains a single [4Fe–4S] cluster and a single siroheme via a bridging sulfur atom from a cysteine residue. The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

Nitrite reductase is found in several organisms and different forms that reduce nitrite to various products. The enzyme displayed contains a siroheme and iron-sulfur cluster to reduce nitrite to ammonia in certain plants. It is found in the stromal space of chloroplasts. Several other types of iron-based enzymes in bacteria reduce nitrite to nitrous oxide. There are also several types of Copper Nitrite Reductases found in many different plants and bacteria.

=='''Mechanism'''==

The electron flow proceeds initially from reduced ferredoxin to the enzyme's [4Fe–4S] cluster and subsequently from the reduced cluster to the siroheme. Since ferredoxin is a one-electron donor, the enzyme must accumulate six electrons in one-electron steps before it can reduce nitrite. Eight protons are also required in the reduction reaction. Reduced ferredoxin binds to the enzyme near the iron-sulfur cluster which becomes reduced. The cluster then transfers an electron to the siroheme. The reduced siroheme binds nitrite. Five more electrons are transferred to siroheme in this way until nitrite is fully reduced.

:::::::::::NO2- + 6Fd(red) + 8H+ → NH3 + 6Fd(ox) + 2H2O

::[[Image:Pathway.jpeg]]

=='''Structure'''==

===Secondary Structures===
Nitrite Reductase has only one chain consisting of 591 residues. There are 33 <scene name='Sandbox_Reserved_460/Helices/1'>helices</scene> (33% of chain) and 33 <scene name='Sandbox_Reserved_460/Beta_sheets/1'>beta strands</scene> (21% of chain). The enzyme is composed of three alpha/beta <scene name='Sandbox_Reserved_460/3domains/1'>domains</scene> which are not as well classified as nitrate reductase.

===Ligands===
<scene name='Sandbox_Reserved_460/Siroheme/1'>Siroheme</scene> is an iron-containing, modified tetrapyrrole similar in structure to both a heme and chlorophyll. It is a heme-like prosthetic group used by nitrite reductase to carry out the six-electron reduction of nitrogen. Nitrite is reduced to ammonia while still bound to siroheme.
The siroheme-iron sulfur cofactor is at the interface of the three domains of the enzyme. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

The <scene name='Sandbox_Reserved_460/Fe-s_cluster/1'>iron-sulfer cluster</scene> is a prosthetic group involved in single electron transfer from reduced ferrodoxin to siroheme.

===Ligand Binding to Active Sites===
* <scene name='Sandbox_Reserved_460/Ac1/3'>AC1</scene> binds Siroheme
* <scene name='Sandbox_Reserved_460/Ac2/3'>AC2</scene> binds Iron-Sulfur Complex
* <scene name='Sandbox_Reserved_460/Ac3/2'>AC3</scene> binds Potassium ion
* <scene name='Sandbox_Reserved_460/Ac4/2'>AC4</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac5/2'>AC5</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac6/2'>AC6</scene> binds Nitrite

=='''References'''==
#Crawford NM: Nitrate: Nutrient and Signal for Plant Growth. The Plant Cell 1995, 7:859-868.
#Schottler MA, Albus CA, Bock R: Photosystem I: Its biogenesis and function in higher plants. Journal of Plant Physiology 2011, 168:1452-1461.
#Vincentz M, Moureaux T, Leydecker MT, Vaucheret H, Caboche M: Regulation of nitrate and nitrite reductase expression in Nicotiana plumbaginifolia leaves by nitrogen and carbon metabolites. The Plant Journal 1993, 3:315-324.
#Campbell WH, Kinghorn Jr: Functional domains of assimilatory nitrate reductases and nitrite reductases. Trends in Biochemical Sciences 1990, 15:315-319.
#Hirasawa M, Knaff DB: Interaction of ferredoxin-linked nitrite reductase with ferredoxin. BBA Protein Structure and Molecular Enzymology 1985, 830:173-180.

Sandbox Reserved 460

2012-05-02T17:15:23Z

Erika England:

{{Sandbox_Reserved_Robert_B_Rose_1}}


<Structure load='3VKP' size='500' frame='true' align='right' caption='Nitrite Reductase' scene='Insert optional scene name here' />

=Nitrite Reductase=
=='''General Information'''==
Nitrogen is an essential element for plant growth and development. Many plants form symbiotic relationships with bacteria and fungi to fix elemental nitrogen from the atmosphere to a deliverable form for the plants to use. Other plants have enzymes that can reduce nitrates in the soil to ammonium in a two step reduction process involving nitrate reductase and nitrite reductase. Without a functional nitrite reductase, the plants accumulate excess nitrites in the cells which are toxic to plants.
=='''Overview'''==

Nitrite reductase is an enzyme that belongs to the Oxidoreductase family for catalyzing the six-electron reduction of nitrite into ammonia, using the reduced ferredoxin as the electron donor. It is a monomeric protein with molecular mass near 63 kDa characterized by a unique <scene name='Sandbox_Reserved_460/Active_site/3'>active site</scene> which contains a single [4Fe–4S] cluster and a single siroheme via a bridging sulfur atom from a cysteine residue. The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

Nitrite reductase is found in several organisms and different forms that reduce nitrite to various products. The enzyme displayed contains a siroheme and iron-sulfur cluster to reduce nitrite to ammonia in certain plants. It is found in the stromal space of chloroplasts. Several other types of iron-based enzymes in bacteria reduce nitrite to nitrous oxide. There are also several types of Copper Nitrite Reductases found in many different plants and bacteria.

=='''Mechanism'''==

The electron flow proceeds initially from reduced ferredoxin to the enzyme's [4Fe–4S] cluster and subsequently from the reduced cluster to the siroheme. Since ferredoxin is a one-electron donor, the enzyme must accumulate six electrons in one-electron steps before it can reduce nitrite. Eight protons are also required in the reduction reaction. Reduced ferredoxin binds to the enzyme near the iron-sulfur cluster which becomes reduced. The cluster then transfers an electron to the siroheme. The reduced siroheme binds nitrite. Five more electrons are transferred to siroheme in this way until nitrite is fully reduced.

:::::::::::NO2- + 6Fd(red) + 8H+ → NH3 + 6Fd(ox) + 2H2O

::[[Image:Pathway.jpeg]]

=='''Structure'''==

===Secondary Structures===
Nitrite Reductase has only one chain consisting of 591 residues. There are 33 <scene name='Sandbox_Reserved_460/Helices/1'>helices</scene> (33% of chain) and 33 <scene name='Sandbox_Reserved_460/Beta_sheets/1'>beta strands</scene> (21% of chain). The enzyme is composed of three alpha/beta <scene name='Sandbox_Reserved_460/3domains/1'>domains</scene> which are not as well classified as nitrate reductase.

===Ligands===
<scene name='Sandbox_Reserved_460/Siroheme/1'>Siroheme</scene> is an iron-containing, modified tetrapyrrole similar in structure to both a heme and chlorophyll. It is a heme-like prosthetic group used by nitrite reductase to carry out the six-electron reduction of nitrogen. Nitrite is reduced to ammonia while still bound to siroheme.
The siroheme-iron sulfur cofactor is at the interface of the three domains of the enzyme. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

The <scene name='Sandbox_Reserved_460/Fe-s_cluster/1'>iron-sulfer cluster</scene> is a prosthetic group involved in single electron transfer from reduced ferrodoxin to siroheme.

===Ligand Binding to Active Sites===
* <scene name='Sandbox_Reserved_460/Ac1/3'>AC1</scene> binds Siroheme
* <scene name='Sandbox_Reserved_460/Ac2/3'>AC2</scene> binds Iron-Sulfur Complex
* <scene name='Sandbox_Reserved_460/Ac3/2'>AC3</scene> binds Potassium ion
* <scene name='Sandbox_Reserved_460/Ac4/2'>AC4</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac5/2'>AC5</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac6/2'>AC6</scene> binds Nitrite

=='''References'''==
#Crawford NM: Nitrate: Nutrient and Signal for Plant Growth. The Plant Cell 1995, 7:859-868.
#Schottler MA, Albus CA, Bock R: Photosystem I: Its biogenesis and function in higher plants. Journal of Plant Physiology 2011, 168:1452-1461.
#Vincentz M, Moureaux T, Leydecker MT, Vaucheret H, Caboche M: Regulation of nitrate and nitrite reductase expression in Nicotiana plumbaginifolia leaves by nitrogen and carbon metabolites. The Plant Journal 1993, 3:315-324.
#Campbell WH, Kinghorn Jr: Functional domains of assimilatory nitrate reductases and nitrite reductases. Trends in Biochemical Sciences 1990, 15:315-319.
#Hirasawa M, Knaff DB: Interaction of ferredoxin-linked nitrite reductase with ferredoxin. BBA Protein Structure and Molecular Enzymology 1985, 830:173-180.

Sandbox Reserved 460

2012-05-02T17:14:15Z

Erika England:

{{Sandbox_Reserved_Robert_B_Rose_1}}


<Structure load='3VKP' size='500' frame='true' align='right' caption='Nitrite Reductase' scene='Insert optional scene name here' />

=Nitrite Reductase=
=='''General Information'''==
Nitrogen is an essential element for plant growth and development. Many plants form symbiotic relationships with bacteria and fungi to fix elemental nitrogen from the atmosphere to a deliverable form for the plants to use. Other plants have enzymes that can reduce nitrates in the soil to ammonium in a two step reduction process involving nitrate reductase and nitrite reductase. Without a functional nitrite reductase, the plants accumulate excess nitrites in the cells which are toxic to plants.
=='''Overview'''==

Nitrite reductase is an enzyme that belongs to the Oxidoreductase family for catalyzing the six-electron reduction of nitrite into ammonia, using the reduced ferredoxin as the electron donor. It is a monomeric protein with molecular mass near 63 kDa characterized by a unique <scene name='Sandbox_Reserved_460/Active_site/3'>active site</scene> which contains a single [4Fe–4S] cluster and a single siroheme via a bridging sulfur atom from a cysteine residue. The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

Nitrite reductase is found in several organisms and different forms that reduce nitrite to various products. The enzyme displayed contains a siroheme and iron-sulfur cluster to reduce nitrite to ammonia in certain plants. It is found in the stromal space of chloroplasts. Several other types of iron-based enzymes in bacteria reduce nitrite to nitrous oxide. There are also several types of Copper Nitrite Reductases found in many different plants and bacteria.

=='''Mechanism'''==

The electron flow proceeds initially from reduced ferredoxin to the enzyme's [4Fe–4S] cluster and subsequently from the reduced cluster to the siroheme. Since ferredoxin is a one-electron donor, the enzyme must accumulate six electrons in one-electron steps before it can reduce nitrite. Eight protons are also required in the reduction reaction. Reduced ferredoxin binds to the enzyme near the iron-sulfur cluster which becomes reduced. The cluster then transfers an electron to the siroheme. The reduced siroheme binds nitrite. Five more electrons are transferred to siroheme in this way until nitrite is fully reduced.

:::NO2- + 6Fd(red) + 8H+ → NH3 + 6Fd(ox) + 2H2O

::[[Image:Pathway.jpeg]]

=='''Structure'''==

===Secondary Structures===
Nitrite Reductase has only one chain consisting of 591 residues. There are 33 <scene name='Sandbox_Reserved_460/Helices/1'>helices</scene> (33% of chain) and 33 <scene name='Sandbox_Reserved_460/Beta_sheets/1'>beta strands</scene> (21% of chain). The enzyme is composed of three alpha/beta <scene name='Sandbox_Reserved_460/3domains/1'>domains</scene> which are not as well classified as nitrate reductase.

===Ligands===
<scene name='Sandbox_Reserved_460/Siroheme/1'>Siroheme</scene> is an iron-containing, modified tetrapyrrole similar in structure to both a heme and chlorophyll. It is a heme-like prosthetic group used by nitrite reductase to carry out the six-electron reduction of nitrogen. Nitrite is reduced to ammonia while still bound to siroheme.
The siroheme-iron sulfur cofactor is at the interface of the three domains of the enzyme. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

The <scene name='Sandbox_Reserved_460/Fe-s_cluster/1'>iron-sulfer cluster</scene> is a prosthetic group involved in single electron transfer from reduced ferrodoxin to siroheme.

===Ligand Binding to Active Sites===
* <scene name='Sandbox_Reserved_460/Ac1/3'>AC1</scene> binds Siroheme
* <scene name='Sandbox_Reserved_460/Ac2/3'>AC2</scene> binds Iron-Sulfur Complex
* <scene name='Sandbox_Reserved_460/Ac3/2'>AC3</scene> binds Potassium ion
* <scene name='Sandbox_Reserved_460/Ac4/2'>AC4</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac5/2'>AC5</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac6/2'>AC6</scene> binds Nitrite

=='''References'''==
#Crawford NM: Nitrate: Nutrient and Signal for Plant Growth. The Plant Cell 1995, 7:859-868.
#Schottler MA, Albus CA, Bock R: Photosystem I: Its biogenesis and function in higher plants. Journal of Plant Physiology 2011, 168:1452-1461.
#Vincentz M, Moureaux T, Leydecker MT, Vaucheret H, Caboche M: Regulation of nitrate and nitrite reductase expression in Nicotiana plumbaginifolia leaves by nitrogen and carbon metabolites. The Plant Journal 1993, 3:315-324.
#Campbell WH, Kinghorn Jr: Functional domains of assimilatory nitrate reductases and nitrite reductases. Trends in Biochemical Sciences 1990, 15:315-319.
#Hirasawa M, Knaff DB: Interaction of ferredoxin-linked nitrite reductase with ferredoxin. BBA Protein Structure and Molecular Enzymology 1985, 830:173-180.

Sandbox Reserved 460

2012-05-02T17:05:25Z

Erika England:

{{Sandbox_Reserved_Robert_B_Rose_1}}


<Structure load='3VKP' size='500' frame='true' align='right' caption='Nitrite Reductase' scene='Insert optional scene name here' />

=Nitrite Reductase=
=='''General Information'''==
Nitrogen is an essential element for plant growth and development. Many plants form symbiotic relationships with bacteria and fungi to fix elemental nitrogen from the atmosphere to a deliverable form for the plants to use. Other plants have enzymes that can reduce nitrates in the soil to ammonium in a two step reduction process involving nitrate reductase and nitrite reductase. Without a functional nitrite reductase, the plants accumulate excess nitrites in the cells which are toxic to plants.
=='''Overview'''==

Nitrite reductase is an enzyme that belongs to the Oxidoreductase family for catalyzing the six-electron reduction of nitrite into ammonia, using the reduced ferredoxin as the electron donor. It is a monomeric protein with molecular mass near 63 kDa characterized by a unique <scene name='Sandbox_Reserved_460/Active_site/3'>active site</scene> which contains a single [4Fe–4S] cluster and a single siroheme via a bridging sulfur atom from a cysteine residue. The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

Nitrite reductase is found in several organisms and different forms that reduce nitrite to various products. The enzyme displayed contains a siroheme and iron-sulfur cluster to reduce nitrite to ammonia in certain plants. It is found in the stromal space of chloroplasts. Several other types of iron-based enzymes in bacteria reduce nitrite to nitrous oxide. There are also several types of Copper Nitrite Reductases found in many different plants and bacteria.

=='''Mechanism'''==

The electron flow proceeds initially from reduced ferredoxin to the enzyme's [4Fe–4S] cluster and subsequently from the reduced cluster to the siroheme. Since ferredoxin is a one-electron donor, the enzyme must accumulate six electrons in one-electron steps before it can reduce nitrite. Eight protons are also required in the reduction reaction. Reduced ferredoxin binds to the enzyme near the iron-sulfur cluster which becomes reduced. The cluster then transfers an electron to the siroheme. The reduced siroheme binds nitrite. Five more electrons are transferred to siroheme in this way until nitrite is fully reduced.

::[[Image:Pathway.jpeg]] NO2- + 6Fd(red) + 8H+ → NH3 + 6Fd(ox) + 2H2O

=='''Structure'''==

===Secondary Structures===
Nitrite Reductase has only one chain consisting of 591 residues. There are 33 <scene name='Sandbox_Reserved_460/Helices/1'>helices</scene> (33% of chain) and 33 <scene name='Sandbox_Reserved_460/Beta_sheets/1'>beta strands</scene> (21% of chain). The enzyme is composed of three alpha/beta <scene name='Sandbox_Reserved_460/3domains/1'>domains</scene> which are not as well classified as nitrate reductase.

===Ligands===
<scene name='Sandbox_Reserved_460/Siroheme/1'>Siroheme</scene> is an iron-containing, modified tetrapyrrole similar in structure to both a heme and chlorophyll. It is a heme-like prosthetic group used by nitrite reductase to carry out the six-electron reduction of nitrogen. Nitrite is reduced to ammonia while still bound to siroheme.
The siroheme-iron sulfur cofactor is at the interface of the three domains of the enzyme. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

Iron-sulfer cluster is a prosthetic group involved in single electron transfer from reduced ferrodoxin to siroheme.

===Ligand Binding to Active Sites===
* <scene name='Sandbox_Reserved_460/Ac1/3'>AC1</scene> binds Siroheme
* <scene name='Sandbox_Reserved_460/Ac2/3'>AC2</scene> binds Iron-Sulfur Complex
* <scene name='Sandbox_Reserved_460/Ac3/2'>AC3</scene> binds Potassium ion
* <scene name='Sandbox_Reserved_460/Ac4/2'>AC4</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac5/2'>AC5</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac6/2'>AC6</scene> binds Nitrite

=='''References'''==
#Crawford NM: Nitrate: Nutrient and Signal for Plant Growth. The Plant Cell 1995, 7:859-868.
#Schottler MA, Albus CA, Bock R: Photosystem I: Its biogenesis and function in higher plants. Journal of Plant Physiology 2011, 168:1452-1461.
#Vincentz M, Moureaux T, Leydecker MT, Vaucheret H, Caboche M: Regulation of nitrate and nitrite reductase expression in Nicotiana plumbaginifolia leaves by nitrogen and carbon metabolites. The Plant Journal 1993, 3:315-324.
#Campbell WH, Kinghorn Jr: Functional domains of assimilatory nitrate reductases and nitrite reductases. Trends in Biochemical Sciences 1990, 15:315-319.
#Hirasawa M, Knaff DB: Interaction of ferredoxin-linked nitrite reductase with ferredoxin. BBA Protein Structure and Molecular Enzymology 1985, 830:173-180.

Sandbox Reserved 460

2012-05-02T00:43:09Z

Erika England:

{{Sandbox_Reserved_Robert_B_Rose_1}}


<Structure load='3VKP' size='500' frame='true' align='right' caption='Nitrite Reductase' scene='Insert optional scene name here' />

=Nitrite Reductase=
=='''General Information'''==
Nitrogen is an essential element for plant growth and development. Many plants form symbiotic relationships with bacteria and fungi to fix elemental nitrogen from the atmosphere to a deliverable form for the plants to use. Other plants have enzymes that can reduce nitrates in the soil to ammonium.
=='''Overview'''==

Nitrite reductase is an enzyme that belongs to the Oxidoreductase family for catalyzing the six-electron reduction of nitrite into ammonia, using the reduced ferredoxin as the electron donor. It is a monomeric protein with molecular mass near 63 kDa characterized by a unique <scene name='Sandbox_Reserved_460/Active_site/3'>active site</scene> which contains a single [4Fe–4S] cluster and a single siroheme (which serves as the binding site for nitrite) via a bridging sulfur atom from a cysteine residue. The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

Nitrite reductase is found in several organisms and different forms that reduce nitrite to various products. The enzyme to the right contains a siroheme and iron-sulfur cluster to reduce nitrite to ammonia in certain plants. It is found in the stromal space of chloroplasts. Several other types of iron-based enzymes in bacteria reduce nitrite to nitrous oxide. There are also several types of Copper Nitrite Reductases found in many different plants and bacteria.

=='''Mechanism'''==

The electron flow proceeds initially from reduced ferredoxin to the enzyme's [4Fe–4S] cluster and subsequently from the reduced cluster to the siroheme. Since ferredoxin is a one-electron donor, the enzyme must accumulate six electrons in one-electron steps before it can reduce nitrite. Eight protons are also required in the reduction reaction. Reduced ferredoxin binds to the enzyme near the iron-sulfur cluster which becomes reduced. The cluster then transfers an electron to the siroheme. The reduced siroheme binds nitrite. Five more electrons are transferred to siroheme this way until nitrite is fully reduced.

::[[Image:Pathway.jpeg]] NO2- + 6Fd(red) + 8H+ → NH3 + 6Fd(ox) + 2H2O

=='''Structure'''==

===Secondary Structures===
Nitrite Reductase has only one chain consisting of 591 residues. There are 33 <scene name='Sandbox_Reserved_460/Helices/1'>helices</scene> (33% of chain) and 33 <scene name='Sandbox_Reserved_460/Beta_sheets/1'>beta strands</scene> (21% of chain). The enzyme is composed of three alpha/beta <scene name='Sandbox_Reserved_460/3domains/1'>domains</scene>.

===Ligands===
<scene name='Sandbox_Reserved_460/Siroheme/1'>Siroheme</scene> is an iron-containing, modified tetrapyrrole similar in structure to both heme and chlorophyll. It is a heme-like prosthetic group used by nitrite reductase to carry out the six-electron reduction of nitrogen. Nitrite is reduced to ammonia while still bound to siroheme.
The siroheme-iron sulfur cofactor is at the interface of the three domains of the enzyme. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

===Ligand Binding to Active Sites===
* <scene name='Sandbox_Reserved_460/Ac1/3'>AC1</scene> binds Siroheme
* <scene name='Sandbox_Reserved_460/Ac2/3'>AC2</scene> binds Iron-Sulfur Complex
* <scene name='Sandbox_Reserved_460/Ac3/2'>AC3</scene> binds Potassium ion
* <scene name='Sandbox_Reserved_460/Ac4/2'>AC4</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac5/2'>AC5</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac6/2'>AC6</scene> binds Nitrite

=='''References'''==
#Crawford NM: Nitrate: Nutrient and Signal for Plant Growth. The Plant Cell 1995, 7:859-868.
#Schottler MA, Albus CA, Bock R: Photosystem I: Its biogenesis and function in higher plants. Journal of Plant Physiology 2011, 168:1452-1461.
#Vincentz M, Moureaux T, Leydecker MT, Vaucheret H, Caboche M: Regulation of nitrate and nitrite reductase expression in Nicotiana plumbaginifolia leaves by nitrogen and carbon metabolites. The Plant Journal 1993, 3:315-324.
#

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Erika England:

{{Sandbox_Reserved_Robert_B_Rose_1}}


<Structure load='3VKP' size='500' frame='true' align='right' caption='Nitrite Reductase' scene='Insert optional scene name here' />

=Nitrite Reductase=
=='''General Information'''==
Nitrogen is an essential element for plant growth and development. Many plants form symbiotic relationships with bacteria and fungi to fix elemental nitrogen from the atmosphere to a deliverable form for the plants to use. Other plants have enzymes that can reduce nitrates in the soil to ammonium.
=='''Overview'''==

Nitrite reductase is an enzyme that belongs to the Oxidoreductase family for catalyzing the six-electron reduction of nitrite into ammonia, using the reduced ferredoxin as the electron donor. It is a monomeric protein with molecular mass near 63 kDa characterized by a unique <scene name='Sandbox_Reserved_460/Active_site/3'>active site</scene> which contains a single [4Fe–4S] cluster and a single siroheme (which serves as the binding site for nitrite) via a bridging sulfur atom from a cysteine residue. The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

Nitrite reductase is found in several organisms and different forms that reduce nitrite to various products. The enzyme to the right contains a siroheme and iron-sulfur cluster to reduce nitrite to ammonia in certain plants. It is found in the stromal space of chloroplasts. Several other types of iron-based enzymes in bacteria reduce nitrite to nitrous oxide. There are also several types of Copper Nitrite Reductases found in many different plants and bacteria.

=='''Mechanism'''==

The electron flow proceeds initially from reduced ferredoxin to the enzyme's [4Fe–4S] cluster and subsequently from the reduced cluster to the siroheme. Since ferredoxin is a one-electron donor, the enzyme must accumulate six electrons in one-electron steps before it can reduce nitrite. Eight protons are also required in the reduction reaction. Reduced ferredoxin binds to the enzyme near the iron-sulfur cluster which becomes reduced. The cluster then transfers an electron to the siroheme. The reduced siroheme binds nitrite. Five more electrons are transferred to siroheme this way until nitrite is fully reduced.

::[[Image:Pathway.jpeg]] NO2- + 6Fd(red) + 8H+ → NH3 + 6Fd(ox) + 2H2O

=='''Structure'''==

===Secondary Structures===
Nitrite Reductase has only one chain consisting of 591 residues. There are 33 <scene name='Sandbox_Reserved_460/Helices/1'>helices</scene> (33% of chain) and 33 <scene name='Sandbox_Reserved_460/Beta_sheets/1'>beta strands</scene> (21% of chain). The enzyme is composed of three alpha/beta <scene name='Sandbox_Reserved_460/3domains/1'>domains</scene>.

===Ligands===
<scene name='Sandbox_Reserved_460/Siroheme/1'>Siroheme</scene> is an iron-containing, modified tetrapyrrole similar in structure to both heme and chlorophyll. It is a heme-like prosthetic group used by nitrite reductase to carry out the six-electron reduction of nitrogen. Nitrite is reduced to ammonia while still bound to siroheme.
The siroheme-iron sulfur cofactor is at the interface of the three domains of the enzyme. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

===Ligand Binding to Active Sites===
* <scene name='Sandbox_Reserved_460/Ac1/3'>AC1</scene> binds Siroheme
* <scene name='Sandbox_Reserved_460/Ac2/3'>AC2</scene> binds Iron-Sulfur Complex
* <scene name='Sandbox_Reserved_460/Ac3/2'>AC3</scene> binds Potassium ion
* <scene name='Sandbox_Reserved_460/Ac4/2'>AC4</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac5/2'>AC5</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac6/2'>AC6</scene> binds Nitrite

=='''References'''==
#Crawford NM: Nitrate: Nutrient and Signal for Plant Growth. The Plant Cell 1995, 7:859-868.

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Erika England:

{{Sandbox_Reserved_Robert_B_Rose_1}}


<Structure load='3VKP' size='500' frame='true' align='right' caption='Nitrite Reductase' scene='Insert optional scene name here' />

=Nitrite Reductase=
=='''General Information'''==
Nitrogen is an essential element for plant growth and development. Many plants form symbiotic relationships with bacteria and fungi to fix elemental nitrogen from the atmosphere to a deliverable form for the plants to use. Other plants have enzymes that can reduce nitrates in the soil to ammonium.
=='''Overview'''==
----
Nitrite reductase is an enzyme that belongs to the Oxidoreductase family for catalyzing the six-electron reduction of nitrite into ammonia, using the reduced ferredoxin as the electron donor. It is a monomeric protein with molecular mass near 63 kDa characterized by a unique <scene name='Sandbox_Reserved_460/Active_site/3'>active site</scene> which contains a single [4Fe–4S] cluster and a single siroheme (which serves as the binding site for nitrite) via a bridging sulfur atom from a cysteine residue. The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

Nitrite reductase is found in several organisms and different forms that reduce nitrite to various products. The enzyme to the right contains a siroheme and iron-sulfur cluster to reduce nitrite to ammonia in certain plants. It is found in the stromal space of chloroplasts. Several other types of iron-based enzymes in bacteria reduce nitrite to nitrous oxide. There are also several types of Copper Nitrite Reductases found in many different plants and bacteria.

=='''Mechanism'''==
----
The electron flow proceeds initially from reduced ferredoxin to the enzyme's [4Fe–4S] cluster and subsequently from the reduced cluster to the siroheme. Since ferredoxin is a one-electron donor, the enzyme must accumulate six electrons in one-electron steps before it can reduce nitrite. Eight protons are also required in the reduction reaction. Reduced ferredoxin binds to the enzyme near the iron-sulfur cluster which becomes reduced. The cluster then transfers an electron to the siroheme. The reduced siroheme binds nitrite. Five more electrons are transferred to siroheme this way until nitrite is fully reduced.
NO2- + 6Fd(red) + 8H+ → NH3 + 6Fd(ox) + 2H2O

::[[Image:Pathway.jpeg]]

=='''Structure'''==
----
===Secondary Structures===
Nitrite Reductase has only one chain consisting of 591 residues. There are 33 <scene name='Sandbox_Reserved_460/Helices/1'>helices</scene> (33% of chain) and 33 <scene name='Sandbox_Reserved_460/Beta_sheets/1'>beta strands</scene> (21% of chain). The enzyme is composed of three <scene name='Sandbox_Reserved_460/3domains/1'>domains</scene>.

===Ligands===
<scene name='Sandbox_Reserved_460/Siroheme/1'>Siroheme</scene> is an iron-containing, modified tetrapyrrole similar in structure to both heme and chlorophyll. It is a heme-like prosthetic group used by nitrite reductase to carry out the six-electron reduction of nitrogen. Nitrite is reduced to ammonia while still bound to siroheme.
The siroheme-iron sulfur cofactor is at the interface of the three domains of the enzyme. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

===Ligand Binding to Active Sites===
* <scene name='Sandbox_Reserved_460/Ac1/3'>AC1</scene> binds Siroheme
* <scene name='Sandbox_Reserved_460/Ac2/3'>AC2</scene> binds Iron-Sulfur Complex
* <scene name='Sandbox_Reserved_460/Ac3/2'>AC3</scene> binds Potassium ion
* <scene name='Sandbox_Reserved_460/Ac4/2'>AC4</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac5/2'>AC5</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac6/2'>AC6</scene> binds Nitrite

=='''References'''==

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Erika England:

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Erika England:

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Erika England:

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Erika England:

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Erika England:

<Structure load='3VKP' size='500' frame='true' align='right' caption='Nitrite Reductase' scene='Insert optional scene name here' />
{{Sandbox_Reserved_Robert_B_Rose_1}}


=Nitrite Reductase=
=='''Overview'''==
----
Nitrite reductase is an enzyme that belongs to the Oxidoreductase family for catalyzing the six-electron reduction of nitrite into ammonia, using the reduced ferredoxin as the electron donor. It is a monomeric protein with molecular mass near 66 kDa characterized by a unique <scene name='Sandbox_Reserved_460/Active_site/3'>active site</scene> which contains a single [4Fe–4S] cluster and a single siroheme (which serves as the binding site for nitrite) via a bridging sulfur atom from a cysteine residue. The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

=='''Mechanism'''==
----
The electron flow proceeds initially from reduced ferredoxin to the enzyme's [4Fe–4S] cluster and subsequently from the reduced cluster to the siroheme. Since ferredoxin is a one-electron donor, the enzyme must accumulate six electrons in one-electron steps before it can reduce nitrite.
[[Image:Pathway.jpeg]]

=='''Structure'''==
----
===Secondary Structures===
Nitrite Reductase has only one chain consisting of 591 residues. There are 33 <scene name='Sandbox_Reserved_460/Helices/1'>helices</scene> (33% of chain) and 33 <scene name='Sandbox_Reserved_460/Beta_sheets/1'>beta strands</scene> (21% of chain).

===Ligands===
Siroheme is an iron-containing isobacteriochlorin, a modified tetrapyrrole similar in structure to both heme and chlorophyll. It is a heme-like prosthetic group used by nitrite reductase to carry out the six-electron reduction of nitrogen. Nitrite is reduced to ammonium while still bound to siroheme.
The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite. It has 3 iron atoms, one of which is in the siroheme.
Has only one chain consisting of 591 residues.
It consists of 33 helices (33% of chain) and 33 beta strands (21% of chain)

===Ligand Binding to Active Sites===
* <scene name='Sandbox_Reserved_460/Ac1/3'>AC1</scene> binds Siroheme
* <scene name='Sandbox_Reserved_460/Ac2/3'>AC2</scene> binds Iron-Sulfur Complex
* <scene name='Sandbox_Reserved_460/Ac3/2'>AC3</scene> binds Potassium ion
* <scene name='Sandbox_Reserved_460/Ac4/2'>AC4</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac5/2'>AC5</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac6/2'>AC6</scene> binds Nitrite

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Erika England:

<Structure load='3VKP' size='500' frame='true' align='right' caption='Nitrite Reductase' scene='Insert optional scene name here' />
{{Sandbox_Reserved_Robert_B_Rose_1}}


=Nitrite Reductase=
==='''Overview'''===
----
Nitrite reductase is an enzyme that belongs to the Oxidoreductase family for catalyzing the six-electron reduction of nitrite into ammonia, using the reduced ferredoxin as the electron donor. It is a monomeric protein with molecular mass near 66 kDa characterized by a unique <scene name='Sandbox_Reserved_460/Active_site/3'>active site</scene> which contains a single [4Fe–4S] cluster and a single siroheme (which serves as the binding site for nitrite) via a bridging sulfur atom from a cysteine residue. The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

==='''Mechanism'''===
----
The electron flow proceeds initially from reduced ferredoxin to the enzyme's [4Fe–4S] cluster and subsequently from the reduced cluster to the siroheme. Since ferredoxin is a one-electron donor, the enzyme must accumulate six electrons in one-electron steps before it can reduce nitrite.
[[Image:Pathway.jpeg]]

==='''Structure'''===
----
====Secondary Structures====
Nitrite Reductase has only one chain consisting of 591 residues. There are 33 <scene name='Sandbox_Reserved_460/Helices/1'>helices</scene> (33% of chain) and 33 <scene name='Sandbox_Reserved_460/Beta_sheets/1'>beta strands</scene> (21% of chain).

====Ligands====
Siroheme is an iron-containing isobacteriochlorin, a modified tetrapyrrole similar in structure to both heme and chlorophyll. It is a heme-like prosthetic group used by nitrite reductase to carry out the six-electron reduction of nitrogen. Nitrite is reduced to ammonium while still bound to siroheme.
The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite. It has 3 iron atoms, one of which is in the siroheme.
Has only one chain consisting of 591 residues.
It consists of 33 helices (33% of chain) and 33 beta strands (21% of chain)

====Ligand Binding to Active Sites====
* <scene name='Sandbox_Reserved_460/Ac1/3'>AC1</scene> binds Siroheme
* <scene name='Sandbox_Reserved_460/Ac2/3'>AC2</scene> binds Iron-Sulfur Complex
* <scene name='Sandbox_Reserved_460/Ac3/2'>AC3</scene> binds Potassium ion
* <scene name='Sandbox_Reserved_460/Ac4/2'>AC4</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac5/2'>AC5</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac6/2'>AC6</scene> binds Nitrite

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Erika England:

<Structure load='3VKP' size='500' frame='true' align='right' caption='Nitrite Reductase' scene='Insert optional scene name here' />
{{Sandbox_Reserved_Robert_B_Rose_1}}


=Nitrite Reductase=
==='''Overview'''===
----
Nitrite reductase is an enzyme that belongs to the Oxidoreductase family for catalyzing the six-electron reduction of nitrite into ammonia, using the reduced ferredoxin as the electron donor. It is a monomeric protein with molecular mass near 66 kDa characterized by a unique <scene name='Sandbox_Reserved_460/Active_site/3'>active site</scene> which contains a single [4Fe–4S] cluster and a single siroheme (which serves as the binding site for nitrite) via a bridging sulfur atom from a cysteine residue. The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

==='''Mechanism'''===
----
The electron flow proceeds initially from reduced ferredoxin to the enzyme's [4Fe–4S] cluster and subsequently from the reduced cluster to the siroheme. Since ferredoxin is a one-electron donor, the enzyme must accumulate six electrons in one-electron steps before it can reduce nitrite.
[[Image:Pathway.jpeg]]
==='''Structure'''===
----
====Ligands====
Siroheme is an iron-containing isobacteriochlorin, a modified tetrapyrrole similar in structure to both heme and chlorophyll. It is a heme-like prosthetic group used by nitrite reductase to carry out the six-electron reduction of nitrogen. Nitrite is reduced to ammonium while still bound to siroheme.
The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite. It has 3 iron atoms, one of which is in the siroheme.
Has only one chain consisting of 591 residues.
It consists of 33 helices (33% of chain) and 33 beta strands (21% of chain)

====Ligand Binding to Active Sites====
* <scene name='Sandbox_Reserved_460/Ac1/3'>AC1</scene> binds Siroheme
* <scene name='Sandbox_Reserved_460/Ac2/3'>AC2</scene> binds Iron-Sulfur Complex
* <scene name='Sandbox_Reserved_460/Ac3/2'>AC3</scene> binds Potassium ion
* <scene name='Sandbox_Reserved_460/Ac4/2'>AC4</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac5/2'>AC5</scene> binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac6/2'>AC6</scene> binds Nitrite

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Erika England:

<Structure load='3VKP' size='500' frame='true' align='right' caption='Nitrite Reductase' scene='Insert optional scene name here' />
{{Sandbox_Reserved_Robert_B_Rose_1}}


==='''Nitrite Reductase'''===
----
Nitrite reductase is an enzyme that belongs to the Oxidoreductase family for catalyzing the six-electron reduction of nitrite into ammonia, using the reduced ferredoxin as the electron donor. It is a monomeric protein with molecular mass near 66 kDa characterized by a unique <scene name='Sandbox_Reserved_460/Active_site/3'>active site</scene> which contains a single [4Fe–4S] cluster and a single siroheme (which serves as the binding site for nitrite) via a bridging sulfur atom from a cysteine residue. The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

==='''Mechanism'''===
----
The electron flow proceeds initially from reduced ferredoxin to the enzyme's [4Fe–4S] cluster and subsequently from the reduced cluster to the siroheme. Since ferredoxin is a one-electron donor, the enzyme must accumulate six electrons in one-electron steps before it can reduce nitrite.
[[Image:Pathway.jpeg]]
==='''Structure'''===
----
====Ligands====
Siroheme is an iron-containing isobacteriochlorin, a modified tetrapyrrole similar in structure to both heme and chlorophyll. It is a heme-like prosthetic group used by nitrite reductase to carry out the six-electron reduction of nitrogen. Nitrite is reduced to ammonium while still bound to siroheme.
The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite. It has 3 iron atoms, one of which is in the siroheme.
Has only one chain consisting of 591 residues.
It consists of 33 helices (33% of chain) and 33 beta strands (21% of chain)

====Ligand Binding to Active Sites====
* <scene name='Sandbox_Reserved_460/Ac1/3'>AC1</scene>binds Siroheme
* <scene name='Sandbox_Reserved_460/Ac2/3'>AC2</scene>binds Iron-Sulfur Complex
* <scene name='Sandbox_Reserved_460/Ac3/2'>AC3</scene>binds Potassium ion
* <scene name='Sandbox_Reserved_460/Ac4/2'>AC4</scene>binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac5/2'>AC5</scene>binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac6/2'>AC6</scene>binds Nitrite

File:Pathway.jpeg

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Erika England:

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Erika England:

<Structure load='3VKP' size='500' frame='true' align='right' caption='Nitrite Reductase' scene='Insert optional scene name here' />
{{Sandbox_Reserved_Robert_B_Rose_1}}


==='''Nitrite Reductase'''===
----
Nitrite reductase is an enzyme that belongs to the Oxidoreductase family for catalyzing the six-electron reduction of nitrite into ammonia, using the reduced ferredoxin as the electron donor. It is a monomeric protein with molecular mass near 66 kDa characterized by a unique <scene name='Sandbox_Reserved_460/Active_site/3'>active site</scene> which contains a single [4Fe–4S] cluster and a single siroheme (which serves as the binding site for nitrite) via a bridging sulfur atom from a cysteine residue. The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

==='''Mechanism'''===
----
The electron flow proceeds initially from reduced ferredoxin to the enzyme's [4Fe–4S] cluster and subsequently from the reduced cluster to the siroheme. Since ferredoxin is a one-electron donor, the enzyme must accumulate six electrons in one-electron steps before it can reduce nitrite.

==='''Structure'''===
----
====Ligands====
Siroheme is an iron-containing isobacteriochlorin, a modified tetrapyrrole similar in structure to both heme and chlorophyll. It is a heme-like prosthetic group used by nitrite reductase to carry out the six-electron reduction of nitrogen. Nitrite is reduced to ammonium while still bound to siroheme.
The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite. It has 3 iron atoms, one of which is in the siroheme.
Has only one chain consisting of 591 residues.
It consists of 33 helices (33% of chain) and 33 beta strands (21% of chain)

====Lingand Binding to Active Sites====
* <scene name='Sandbox_Reserved_460/Ac1/3'>AC1</scene>binds Siroheme
* <scene name='Sandbox_Reserved_460/Ac2/3'>AC2</scene>binds Iron-Sulfur Complex
* <scene name='Sandbox_Reserved_460/Ac3/2'>AC3</scene>binds Potassium ion
* <scene name='Sandbox_Reserved_460/Ac4/2'>AC4</scene>binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac5/2'>AC5</scene>binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac6/2'>AC6</scene>binds Nitrite

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Erika England:

<Structure load='3VKP' size='500' frame='true' align='right' caption='Nitrite Reductase' scene='Insert optional scene name here' />
{{Sandbox_Reserved_Robert_B_Rose_1}}


==='''Nitrite Reductase'''===
----
Nitrite reductase is an enzyme that belongs to the Oxidoreductase family for catalyzing the six-electron reduction of nitrite into ammonia, using the reduced ferredoxin as the electron donor. It is a monomeric protein with molecular mass near 66 kDa characterized by a unique <scene name='Sandbox_Reserved_460/Active_site/3'>active site</scene> which contains a single [4Fe–4S] cluster and a single siroheme (which serves as the binding site for nitrite) via a bridging sulfur atom from a cysteine residue. The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

==='''Mechanism'''===
----
The electron flow proceeds initially from reduced ferredoxin to the enzyme's [4Fe–4S] cluster and subsequently from the reduced cluster to the siroheme. Since ferredoxin is a one-electron donor, the enzyme must accumulate six electrons in one-electron steps before it can reduce nitrite.

==='''Structure'''===
----
Siroheme is an iron-containing isobacteriochlorin, a modified tetrapyrrole similar in structure to both heme and chlorophyll. It is a heme-like prosthetic group used by nitrite reductase to carry out the six-electron reduction of nitrogen. Nitrite is reduced to ammonium while still bound to siroheme.
The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite. It has 3 iron atoms, one of which is in the siroheme.
Has only one chain consisting of 591 residues.
It consists of 33 helices (33% of chain) and 33 beta strands (21% of chain)

====Lingand Binding to Active Sites====
* <scene name='Sandbox_Reserved_460/Ac1/3'>AC1</scene>binds Siroheme
* <scene name='Sandbox_Reserved_460/Ac2/3'>AC2</scene>binds Iron-Sulfur Complex
* <scene name='Sandbox_Reserved_460/Ac3/2'>AC3</scene>binds Potassium ion
* <scene name='Sandbox_Reserved_460/Ac4/2'>AC4</scene>binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac5/2'>AC5</scene>binds Chloride ion
* <scene name='Sandbox_Reserved_460/Ac6/2'>AC6</scene>binds Nitrite

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Erika England:

<Structure load='3VKP' size='500' frame='true' align='right' caption='Nitrite Reductase' scene='Insert optional scene name here' />
{{Sandbox_Reserved_Robert_B_Rose_1}}


==='''Nitrite Reductase'''===
----
Nitrite reductase is an enzyme that belongs to the Oxidoreductase family for catalyzing the six-electron reduction of nitrite into ammonia, using the reduced ferredoxin as the electron donor. It is a monomeric protein with molecular mass near 66 kDa characterized by a unique <scene name='Sandbox_Reserved_460/Active_site/3'>active site</scene> which contains a single [4Fe–4S] cluster and a single siroheme (which serves as the binding site for nitrite) via a bridging sulfur atom from a cysteine residue. The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

==='''Mechanism'''===
----
The electron flow proceeds initially from reduced ferredoxin to the enzyme's [4Fe–4S] cluster and subsequently from the reduced cluster to the siroheme. Since ferredoxin is a one-electron donor, the enzyme must accumulate six electrons in one-electron steps before it can reduce nitrite.

==='''Structure'''===
----
Siroheme is an iron-containing isobacteriochlorin, a modified tetrapyrrole similar in structure to both heme and chlorophyll. It is a heme-like prosthetic group used by nitrite reductase to carry out the six-electron reduction of nitrogen. Nitrite is reduced to ammonium while still bound to siroheme.
The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite. It has 3 iron atoms, one of which is in the siroheme.
Has only one chain consisting of 591 residues.
It consists of 33 helices (33% of chain) and 33 beta strands (21% of chain)

====Lingand Binding to Active Sites====

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Erika England:

<Structure load='3VKP' size='500' frame='true' align='right' caption='Nitrite Reductase' scene='Insert optional scene name here' />
{{Sandbox_Reserved_Robert_B_Rose_1}}


==='''Nitrite Reductase'''===
----
Nitrite reductase is an enzyme that belongs to the Oxidoreductase family for catalyzing the six-electron reduction of nitrite into ammonia, using the reduced ferredoxin as the electron donor. It is a monomeric protein with molecular mass near 66 kDa characterized by a unique <scene name='Sandbox_Reserved_460/Active_site/3'>active site</scene> which contains a single [4Fe–4S] cluster and a single siroheme (which serves as the binding site for nitrite) via a bridging sulfur atom from a cysteine residue. The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

==='''Mechanism'''===
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The electron flow proceeds initially from reduced ferredoxin to the enzyme's [4Fe–4S] cluster and subsequently from the reduced cluster to the siroheme. Since ferredoxin is a one-electron donor, the enzyme must accumulate six electrons in one-electron steps before it can reduce nitrite.

==='''Structure'''===
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Siroheme is an iron-containing isobacteriochlorin, a modified tetrapyrrole similar in structure to both heme and chlorophyll. It is a heme-like prosthetic group used by nitrite reductase to carry out the six-electron reduction of nitrogen. Nitrite is reduced to ammonium while still bound to siroheme.
The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite. It has 3 iron atoms, one of which is in the siroheme.
Has only one chain consisting of 591 residues.
It consists of 33 helices (33% of chain) and 33 beta strands (21% of chain)

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2012-05-01T14:14:58Z

Erika England:

<Structure load='3VKP' size='500' frame='true' align='right' caption='Nitrite Reductase' scene='Insert optional scene name here' />
{{Sandbox_Reserved_Robert_B_Rose_1}}


==='''Nitrite Reductase'''===
----
Nitrite reductase is an enzyme that belongs to the Oxidoreductase family for catalyzing the six-electron reduction of nitrite into ammonia, using the reduced ferredoxin as the electron donor. It is a monomeric protein with molecular mass near 66 kDa characterized by a unique active site which contains a single <scene name='Sandbox_Reserved_460/Active_site/1'>[4Fe-4S] cluster</scene> and a single siroheme (which serves as the binding site for nitrite) via a bridging sulfur atom from a cysteine residue. The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite.

==='''Mechanism'''===
----
The electron flow proceeds initially from reduced ferredoxin to the enzyme's [4Fe–4S] cluster and subsequently from the reduced cluster to the siroheme. Since ferredoxin is a one-electron donor, the enzyme must accumulate six electrons in one-electron steps before it can reduce nitrite.

==='''Structure'''===
----
Siroheme is an iron-containing isobacteriochlorin, a modified tetrapyrrole similar in structure to both heme and chlorophyll. It is a heme-like prosthetic group used by nitrite reductase to carry out the six-electron reduction of nitrogen. Nitrite is reduced to ammonium while still bound to siroheme.
The protein has a globular fold consisting of 3 alpha/beta domains with the siroheme-iron sulfur cofactor at the interface of the three domains. The siroheme is surrounded by several ionizable amino acid residues that facilitate the binding and subsequent reduction of nitrite. It has 3 iron atoms, one of which is in the siroheme.
Has only one chain consisting of 591 residues.
It consists of 33 helices (33% of chain) and 33 beta strands (21% of chain)

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2012-05-01T14:10:52Z

Erika England:

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2012-05-01T14:04:16Z

Erika England:

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Erika England:

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2012-04-30T21:19:07Z

Erika England:

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2012-04-30T20:33:07Z

Erika England:

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2012-04-30T19:44:28Z

Erika England:

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2012-03-29T12:25:46Z

Erika England:

{{Sandbox_Reserved_Robert_B_Rose_1}}

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