Sandbox Reserved 335: Difference between revisions

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== Introduction ==

[http://en.wikipedia.org/wiki/Cytochrome Cytochromes] are a class of heme-containing proteins that are generally membrane-bound. They are soluble proteins<ref name=main /> found in bacteria and the mitochondria of eukaryotic organisms, and are known as respiratory pigments because they are involved in electron transfer in various electron transport chains.<ref name="heme">PMID:14871137</ref> Cytochromes can be categorized into three different types, all based on the type of prosthetic heme group the cytochrome contains. Cytochrome ''c'' is named such because it contains the heme ''c''

[http://en.wikipedia.org/wiki/Cytochrome Cytochromes] are a class of heme-containing proteins that are generally membrane-bound. They are soluble proteins<ref name=main /> found in bacteria and the mitochondria of eukaryotic organisms, and are known as respiratory pigments because they are involved in electron transfer in various electron transport chains.<ref name="heme">PMID:14871137</ref> Cytochromes can be categorized into three different types, all based on the type of prosthetic heme group the cytochrome contains. Cytochrome ''c'' is named such because it contains the heme ''c'', which is distinguished from hemes ''a'', ''b'', and ''d'' by its coordination to the protein scaffold by cysteinyl residues.<ref name=heme />

Cyt ''c'' has been split into four classes<ref name=”amb”>PMID:1646017</ref>, Class I containing single domain C-type cytochromes of which there has been at least six classes found in prokaryotes such as [http://en.wikipedia.org/wiki/Desulfovibrio ''Desulfovibrio desulfuricans''], [http://en.wikipedia.org/wiki/Rhodospirillum_rubrum ''Rhodospirillum rubrum''], and ''Rhodothermus marinus''.

=== ''Rhodothermus marinus'' ===

''Rhodothermus marinus'' is a Gram-negative bacterium in the class Sphingobacteria, in phylum Bacteroidetes. These bacteria are thermophilic, obligate aerobes that have been previously isolated from shallow-water submarine hot springs located in Iceland.<ref name="bacteria">Alfredsson GA, Kristjansson JK, Hjörleifsdottir S, Stetter, KO. Rhodothermus marinus, gen. nov., sp. nov., a thermophilic, halophilic bacterium from submarine hot springs in Iceland. J Gen Microbiol. 1988 Feb;134(2):299-306.</ref>

''Rhodothermus marinus'' is a Gram-negative bacterium in the class Sphingobacteria, in phylum Bacteroidetes. These bacteria are thermophilic, obligate aerobes that have been previously isolated from shallow-water submarine hot springs located in Iceland.<ref name="bacteria">Alfredsson GA, Kristjansson JK, Hjörleifsdottir S, Stetter, KO. Rhodothermus marinus, gen. nov., sp. nov., a thermophilic, halophilic bacterium from submarine hot springs in Iceland. J Gen Microbiol. 1988 Feb;134(2):299-306.</ref> ''R. marinus'' monoheme cyt ''c'' (''Rm''cyt''c'') was

== Structure and Function ==

All members in the C-type cytochrome superfamily contain a heme prosthetic group that is covalently attached to the protein via two thioether bonds to cysteine residues~~, and~~ most cytochromes ''c'' occur in a CXXCH motif, where a histidine residue is one of the two axial ligands of the heme iron.<ref name=main>PMID:18855424</ref><ref name=heme /> The other axial position, in monoheme cytochromes ''c'', may be left vacant or be occupied by histidine or methionine residues, but can sometimes be occupied by cysteine or leucine residues.<ref name=main />. The typical monoheme cyt ''c'' fold is formed by helices <scene name='Sandbox_Reserved_335/Helices/1'>A, C, and E</scene>. In ''Rm''cyt''c'', there are seven α-helices,

All members in the C-type cytochrome superfamily contain a heme prosthetic group that is covalently attached to the protein via two thioether bonds to cysteine residues; most cytochromes ''c'' occur in a '''CXXCH motif''', where a histidine residue is one of the two axial ligands of the heme iron.<ref name=main>PMID:18855424</ref><ref name=heme /> The other axial position, in monoheme cytochromes ''c'', may be left vacant or be occupied by histidine or methionine residues, but can sometimes be occupied by cysteine or leucine residues.<ref name=main />. The typical monoheme cyt ''c'' fold is formed by helices <scene name='Sandbox_Reserved_335/Helices/1'>A, C, and E</scene>. In ''Rm''cyt''c'' there are seven α-helices that are folded around the porphyrin ring, all connected by random coils.<ref name=main />

Monoheme cytochromes ''c'' are involved in electron transport chains in both prokaryotes and eukaryotic mitochondria.<ref name=main /> They mediate the transfer of electrons mainly from the ''bc''1 complexes, or their analogs, in the [http://en.wikipedia.org/wiki/Electron_transport_chain electron transport chain] to heme-copper oxygen reductases (HCOs) during [http://en.wikipedia.org/wiki/Oxidative_phosphorylation oxidative phosphorylation]. Heme ''c'' containing domains are often found fused to other protein domains such as these HCOs, including the ''caa''3 oxygen reductases<ref name=main /><ref>PMID:14691678</ref>; these enzymes are membrane-bound and catalyze the reduction of O2 to water.<ref>PMID:11334784</ref> In addition to being involved in the electron transport systems in oxidative phosphorylation, monoheme cyt ''c'' has also been seen to participate in the electron transport chain of [http://en.wikipedia.org/wiki/Photosynthesis photosynthesis].<ref name=main />

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 == Introduction ==
-[http://en.wikipedia.org/wiki/Cytochrome Cytochromes] are a class of heme-containing proteins that are generally membrane-bound. They are soluble proteins<ref name=main /> found in bacteria and the mitochondria of eukaryotic organisms, and are known as respiratory pigments because they are involved in electron transfer in various electron transport chains.<ref name="heme">PMID:14871137</ref> Cytochromes can be categorized into three different types, all based on the type of prosthetic heme group the cytochrome contains. Cytochrome ''c'' is named such because it contains the heme ''c''
+[http://en.wikipedia.org/wiki/Cytochrome Cytochromes] are a class of heme-containing proteins that are generally membrane-bound. They are soluble proteins<ref name=main /> found in bacteria and the mitochondria of eukaryotic organisms, and are known as respiratory pigments because they are involved in electron transfer in various electron transport chains.<ref name="heme">PMID:14871137</ref> Cytochromes can be categorized into three different types, all based on the type of prosthetic heme group the cytochrome contains. Cytochrome ''c'' is named such because it contains the heme ''c'', which is distinguished from hemes ''a'', ''b'', and ''d'' by its coordination to the protein scaffold by cysteinyl residues.<ref name=heme />
+Cyt ''c'' has been split into four classes<ref name=”amb”>PMID:1646017</ref>, Class I containing single domain C-type cytochromes of which there has been at least six classes found in prokaryotes such as [http://en.wikipedia.org/wiki/Desulfovibrio ''Desulfovibrio desulfuricans''], [http://en.wikipedia.org/wiki/Rhodospirillum_rubrum ''Rhodospirillum rubrum''], and ''Rhodothermus marinus''.
 === ''Rhodothermus marinus'' ===
-''Rhodothermus marinus'' is a Gram-negative bacterium in the class Sphingobacteria, in phylum Bacteroidetes. These bacteria are thermophilic, obligate aerobes that have been previously isolated from shallow-water submarine hot springs located in Iceland.<ref name="bacteria">Alfredsson GA, Kristjansson JK, Hjörleifsdottir S, Stetter, KO. Rhodothermus marinus, gen. nov., sp. nov., a thermophilic, halophilic bacterium from submarine hot springs in Iceland. J Gen Microbiol. 1988 Feb;134(2):299-306.</ref>
+''Rhodothermus marinus'' is a Gram-negative bacterium in the class Sphingobacteria, in phylum Bacteroidetes. These bacteria are thermophilic, obligate aerobes that have been previously isolated from shallow-water submarine hot springs located in Iceland.<ref name="bacteria">Alfredsson GA, Kristjansson JK, Hjörleifsdottir S, Stetter, KO. Rhodothermus marinus, gen. nov., sp. nov., a thermophilic, halophilic bacterium from submarine hot springs in Iceland. J Gen Microbiol. 1988 Feb;134(2):299-306.</ref> ''R. marinus'' monoheme cyt ''c'' (''Rm''cyt''c'') was
 == Structure and Function ==
-All members in the C-type cytochrome superfamily contain a heme prosthetic group that is covalently attached to the protein via two thioether bonds to cysteine residues, and most cytochromes ''c'' occur in a CXXCH motif, where a histidine residue is one of the two axial ligands of the heme iron.<ref name=main>PMID:18855424</ref><ref name=heme /> The other axial position, in monoheme cytochromes ''c'', may be left vacant or be occupied by histidine or methionine residues, but can sometimes be occupied by cysteine or leucine residues.<ref name=main />. The typical monoheme cyt ''c'' fold is formed by helices <scene name='Sandbox_Reserved_335/Helices/1'>A, C, and E</scene>. In ''Rm''cyt''c'', there are seven α-helices,
+All members in the C-type cytochrome superfamily contain a heme prosthetic group that is covalently attached to the protein via two thioether bonds to cysteine residues; most cytochromes ''c'' occur in a '''CXXCH motif''', where a histidine residue is one of the two axial ligands of the heme iron.<ref name=main>PMID:18855424</ref><ref name=heme /> The other axial position, in monoheme cytochromes ''c'', may be left vacant or be occupied by histidine or methionine residues, but can sometimes be occupied by cysteine or leucine residues.<ref name=main />. The typical monoheme cyt ''c'' fold is formed by helices <scene name='Sandbox_Reserved_335/Helices/1'>A, C, and E</scene>. In ''Rm''cyt''c'' there are seven α-helices that are folded around the porphyrin ring, all connected by random coils.<ref name=main />
 Monoheme cytochromes ''c'' are involved in electron transport chains in both prokaryotes and eukaryotic mitochondria.<ref name=main /> They mediate the transfer of electrons mainly from the ''bc''<sub>1</sub> complexes, or their analogs, in the [http://en.wikipedia.org/wiki/Electron_transport_chain electron transport chain] to heme-copper oxygen reductases (HCOs) during [http://en.wikipedia.org/wiki/Oxidative_phosphorylation oxidative phosphorylation]. Heme ''c'' containing domains are often found fused to other protein domains such as these HCOs, including the ''caa''<sub>3</sub> oxygen reductases<ref name=main /><ref>PMID:14691678</ref>; these enzymes are membrane-bound and catalyze the reduction of O<sub>2</sub> to water.<ref>PMID:11334784</ref> In addition to being involved in the electron transport systems in oxidative phosphorylation, monoheme cyt ''c'' has also been seen to participate in the electron transport chain of [http://en.wikipedia.org/wiki/Photosynthesis photosynthesis].<ref name=main />