Sandbox Reserved 460: Difference between revisions
From Proteopedia
Jump to navigationJump to search
No edit summary |
No edit summary |
||
| Line 4: | Line 4: | ||
=Nitrite Reductase= | =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. | 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. | 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]] | [[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). | 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. | 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. | 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. | ||
| Line 24: | Line 24: | ||
It consists of 33 helices (33% of chain) and 33 beta strands (21% of chain) | 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/Ac1/3'>AC1</scene> binds Siroheme | ||
* <scene name='Sandbox_Reserved_460/Ac2/3'>AC2</scene> binds Iron-Sulfur Complex | * <scene name='Sandbox_Reserved_460/Ac2/3'>AC2</scene> binds Iron-Sulfur Complex | ||
