View source for Cytochrome c

<StructureSection load='' size='350' side='right' scene='Cytochrome_c/Cyt_c/1' caption='Cytochrome c with heme complex with sulfate (PDB code [[3cp5]])'>
The '''cytochrome ''c''''' (cyt ''c'') proteins are a superfamily belonging to the class of [http://en.wikipedia.org/wiki/All-α_proteins all-α proteins], which are denoted as such by having an α-helical core. Each protein in this superfamily also contains one or more covalently-bound [http://en.wikipedia.org/wiki/Heme heme prosthetic groups].<ref>PMID:11697912</ref><ref name=main /> The cyt ''c'' superfamily contains many different families, some of which are better characterized than others. These families include monodomain and multi-domain C-type cytochromes, such as [http://proteopedia.org/wiki/index.php/1etp cyt c4], a diheme C-type cytochrome, and [http://proteopedia.org/wiki/index.php/2ozy NrfB], a pentaheme C-type cytochrome. In particular, the monoheme cyt ''c'' from ''Rhodothermus marinus'' has been previously studied and provides an excellent example of how some protein characteristics and structures can be extremely diverse, yet conserved, through evolution.<br />  For details on decaheme cyt see [[MtrF]].<br />  For details on Cyt c7 see [[Cytochrome c 7]].

== Introduction ==

[http://en.wikipedia.org/wiki/Cytochrome Cytochromes] are a class of heme-containing proteins found in bacteria and the mitochondria of eukaryotes.<ref name=main /> These proteins are generally membrane-bound and are known as respiratory pigments because they are involved in various electron transport systems in oxidative phosphorylation.<ref name="heme">PMID:14871137</ref> Cytochromes can be categorized into several different types, three of which are based on the type of heme group the cytochrome contains: cytochromes ''a'', ''b'' and ''d'' contain heme ''a'', ''b'' and ''d'', respectively.<ref name=amb /> Cytochrome ''c'' is named such because it contains the heme ''c'', but is mainly distinguished from cytochromes ''a'', ''b'' and ''d'' due to the heme being coordinated with the protein scaffold by cysteinyl residues covalently bound to either one or both of the heme's vinyl side chains.<ref name=heme /> 

Cyt ''c'' has been split into four classes.<ref name=amb>PMID:1646017</ref> Class I contains soluble, low spin<ref name=main /> single domain C-type cytochromes, of which there has been at least six subclasses found in prokaryotes including [http://en.wikipedia.org/wiki/Desulfovibrio ''Desulfovibrio desulfuricans''], [http://en.wikipedia.org/wiki/Rhodospirillum_rubrum ''Rhodospirillum rubrum''], and ''Rhodothermus marinus''. Cyt ''c'' in this class have a single heme attached close to the N-terminus of the polypeptide, with a methionine residue being the sixth iron coordination site. Class II contains higher spin-state cytochromes ''c'', such as cyt ''c''', with the heme being attached closer to the C-terminus. Class III contains cytochromes with multiple heme groups; these proteins have lower redox potentials compared to the other three classes<ref name=amb />. Finally, Class IV is comprised of more complex proteins with higher molecular weights containing heme ''c'' as well as other prosthetic groups.<ref name=class>Cookson DJ, Moore GR, Pitt RC, Williams RJP, Campbell ID, Ambler RP, Bruschi M, Le Gall J. Structural homology of cytochromes c. Eur J Biochem. 1978 Feb;83(1):261-75.</ref>

== ''Rhodothermus marinus'' cytochrome ''c'' ==

== Structure ==

<scene name='Sandbox_Reserved_335/Heme/1'>'Figure 1. The heme group of monoheme cytochrome ''c'' purified from ''Rhodothermus marinus''</scene>

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 <scene name='Sandbox_Reserved_335/Motif/1'>CXXCH motif</scene> where the histidine residue is one of the two axial ligands of the heme iron.<ref name=main>PMID:18855424</ref><ref name=heme /> In monoheme cytochromes ''c'', the other axial position may be left vacant or be occupied by histidine or methionine residues; however, it can sometimes be occupied by cysteine or lysine residues.<ref name=main />. In ''Rm''cyt''c'', XX represents a threonine (Thr46) and an alanine residue (Ala47) that help form the loop 2 structure.

[[Image:heme.gif |frame|left| Figure 2. The tetrapyrrolic heme prosthetic group that can either be covalently attached to or closely associated with various proteins, such as cytochromes and other globin proteins. In ''Rm''cyt''c'', R2 is an ethyl group covalently attached to Cys 45, and R3 is a methyl group covalently attached to Cys48.]]
{{Clear}}
The typical monoheme cyt ''c'' fold is formed by helices <scene name='Sandbox_Reserved_335/Helices/4'>A, C, and E</scene>. ''Rm''cyt''c'' contains seven α-helices that are folded around the heme, all connected by random coils.<ref name=main /> The heme group is axially coordinated by <scene name='Sandbox_Reserved_335/Axial/6'>His49 and Met100</scene>, and the disulfide linkages exist at <scene name='Sandbox_Reserved_335/Cys/1'>Cys45 and Cys48</scene>. The heme group in ''Rm''cyt''c'' is almost completely shielded from solvent due to it being in a mostly hydrophobic pocket. This pocket is formed in part by the seven helices surrounding the ring, but also by two structures that are uncommon in other cytochromes ''c''. First, a 21 amino acid extension of the N-terminal exists, forming <scene name='Sandbox_Reserved_335/Uncommon1/2'>α-helix A' and loop 1</scene>, which wraps around the back of the polypeptide.<ref name=main /> An extension resembling such has only been seen in ''Thermus thermophilus''; however, the extension occurs at the C-terminus rather than the N-terminus.<ref>doi:10.1006/jmbi.1997.1181</ref> A second rarity is that of <scene name='Sandbox_Reserved_335/Uncommon2/2'>helix B'</scene>, inserted between helix D and loop 3, that shields the bottom part of the heme from any solvent.<ref name=main /> In cytochrome ''c''<sub>2</sub> as well as mitochondrial cyt ''c'', a similar yet shorter helix was found, though this helix was present at a different place in the primary sequence. Also, instead of helix B', ''T. thermophilus'' contains a two-stranded [http://en.wikipedia.org/wiki/Beta_sheet β-sheet].<ref name=main /> One final note is the number of <scene name='Sandbox_Reserved_335/Met/1'>methionine</scene> residues that ''Rm''cyt''c'' contains. In general, cyt ''c'' contains about two methionines whereas ''Rm''cyt''c'' contains seven, located on the left of the heme.<ref name=main />

As determined by X-ray crystallography, the ''Rm''cyt''c'' structure was found to contain a sulfate ion coordinated to Glu122 via hydrogen bonding to the protonated carboxylate oxygen. In the protein complex, this ion has been seen to mediate crystal contact between neighbouring protein molecules.<ref name=main /> 

The observation of these structural motifs in other C-type cytochromes can support the divergent evolution of cytochromes ''c''.<ref name=main /> These motifs are present in a number of different bacteria and are seen in similar regions of the secondary structure; however, they exist in the primary sequence in places distinct to the phylum. For example, monoheme cytochromes ''c'' in the rest of the Bacteroidetes phylum have an N-terminus extension that is highly conserved to that of ''Rm''cyt''c'', and the regions in the primary structure that correspond to these secondary motifs are not observed in other bacterial phyla.<ref name=main /> Also, due to these motifs being absent from other phyla, the Bacteroidetes monoheme cyt ''c'' has been said to form a new subfamily of cyt ''c''.

== Function ==

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 to heme-copper oxygen reductases (HCOs) in the [http://en.wikipedia.org/wiki/Electron_transport_chain electron transport chain] of [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 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 /> Cytochrome ''c'' has also been determined to be a major signalling molecule in the apoptotic pathways.

== Electron transport chain ==

In the electron transport chain (ETC), cyt ''c'' shuttles electrons between the respiratory complexes III and IV; complex III is the cytochrome ''bc''<sub>1</sub> complex and IV is cyt ''c'' oxidase. Initially, the heme iron in cyt ''c'' is in the reduced, Fe<sup>3+</sup> state; this allows for the uptake of one electron, oxidizing the iron to the Fe<sup>2+</sup> state.<ref name='etc'>Karp, Gerald (2008). Cell and Molecular Biology (5th edition). Hoboken, NJ: John Wiley & Sons. ISBN 978-0470042175.</ref> The ETC in eukaryotes is quite simple compared to that of prokaryotes (Figure 3). 
[[Image:Etc.gif |frame|left|thumb|300px| Figure 3. The electron transport chain of a) eukaryotes as compared to b) prokaryotes.]] 

In prokaryotic systems, electrons can enter the ETC at a number of places and multiple donors can be in play; however, the underlying transport system remains the same. Electrons are ultimately transferred from donor to various redox complexes including the ''bc''<sub>1</sub> complex and cytochrome ''c'', and finally to a terminal electron acceptor such as molecular oxygen in eukaryotes.<ref name=etc />

The cytochrome oxidase reaction accounts for nearly 90% of all oxygen uptake in most cells.<ref name=etc /> Due to the large role of cytochromes within the ETC, it would be highly detrimental to the cell if any inhibitors were to be present in the organism. Cyanide and azide bind tightly to the cytochrome oxidase complex, halting electron transport and reducing the overall ATP production.<ref name=etc />

== Apoptosis ==

In all organisms, cells undergo [http://en.wikipedia.org/wiki/Apoptosis apoptosis], or programmed cell death, by which there is an extrinsic and an intrinsic pathway. The extrinsic pathway involves an immune response by killer lymphocytes, and once the lymphocyte has been bound to the target cell, an apoptotic cascade occurs.<ref name=etc /> The intrinsic pathway includes cyt ''c'', present in the intermembrane space of mitochondria. In this pathway, the presence of an apoptotic stimulus causes cyt ''c'' to be released into the cytosol. Cytochrome ''c'' in the cytosol now can be recognized and bound to various apoptotic factors, activating them and forming the [http://en.wikipedia.org/wiki/Apoptosome apoptosome]. The apoptosome recruits [http://en.wikipedia.org/wiki/Caspase caspases], which are activated and result in a caspase cascade to proceed with apoptosis.<ref name=etc />
 
Cytochrome ''c'' is required for the intrinsic apoptotic process to function properly. Such as with the electron transport chain, a mutation affecting cyt ''c'' or other structures in apoptosis could cause either an increase or a decrease in the rate of apoptosis.

==Structural and kinetic studies of imidazole binding to two members of the cytochrome c6 family reveal an important role for a conserved heme pocket residue<ref>DOI 10.1007/s00775-011-0758-y</ref>==

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<scene name='Journal:JBIC:7/Cv/4'>Cytochrome c6</scene> is a member of the class I family of c-type cytochromes with a distinctive <scene name='Journal:JBIC:7/Cv/5'>α-helical fold</scene> and a <scene name='Journal:JBIC:7/Cv/6'>methionine and histidine residue serving as axial heme iron ligands</scene>. They function in the photosynthetic electron transport chain of cyanobacteria where they shuttle an electron from the cytochrome b6f complex to photosystem I. Structures of numerous cytochrome ''c''<sub>6</sub> proteins have been determined and all have the <scene name='Journal:JBIC:7/Cv/7'>methionine ligand coordinating to the iron</scene>. In the present work we have solved the structure of the '''Q51V''' site-directed variant of ''Phormidium laminosum'' cytochrome ''c''<sub>6</sub>. This project is part of a study that is aimed at gaining insight into protein factors which modulate the heme mid-point redox potential in the cytochrome ''c''<sub>6</sub> family. The '''Q51V''' variant has been shown to tune over 100 mV of heme redox potential, which for a single heme pocket mutation is very significant and has consequences for function.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;The '''Q51V''' structure confirms that the <scene name='Journal:JBIC:7/Cv/8'>Val replacing the Gln</scene> has the same side-chain orientation in the heme pocket as found in other cytochrome ''c''<sub>6</sub> proteins, that naturally have a Val at this position. The significance of this structure is that the <scene name='Journal:JBIC:7/Cv/14'>axial heme iron methionine is dissociated</scene> and an <scene name='Journal:JBIC:7/Cv/15'>exogenous ligand present in the crystallisation solution, imidazole, is now bound to the heme iron</scene>. Two other structures of imidazole cyt c-adducts have been reported, but neither appear to undergo the <scene name='Journal:JBIC:7/Cv/17'>large structural changes  seen in the Q51V structure</scene>. Both protein and heme structural changes are observed, with the later centered on a <scene name='Journal:JBIC:7/Cv/22'>180 degree rotation around the CA atom of the two heme propionate groups</scene> accompanied by the <scene name='Journal:JBIC:7/Cv/20'>upward movement of an alpha helix</scene> and the <scene name='Journal:JBIC:7/Cv/21'>displacement of two loop regions</scene>.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Protein (un)folding studies on cytochrome c have revealed that (un)folding involves structural units called 'foldons'. The regions in the Q51V imidazole-adduct where structural changes occur map well to the two foldons predicted to unfold first in cytochrome c. Thus <scene name='Journal:JBIC:7/Cv/14'>imidazole triggers the release of the methionine ligand in the Q51V variant</scene>, leading to the formation of an early unfolding intermediate that is stabilised by <scene name='Journal:JBIC:7/Cv/15'>imidazole binding to the vacant heme iron coordination position</scene>, enabling it to be captured in the crystalline form.  

==Structural model of the [Fe]-hydrogenase/cytochrome C553 complex combining NMR and soft-docking<ref>PMID:10748163</ref>==
The <scene name='1e08/1e08-cofactors/1'>complex</scene> shows the specific interaction of the hydrogenase (light blue) with the cytochrome (pink), revealing the path of electron transport from the <scene name='1e08/1e08-activecluster/3'>active site metal cluster</scene>, through three iron-sulfur clusters, and ending in the cytochrome heme (colored red). Two <scene name='1e08/1e08-cys/2'>cysteine amino acids at the interface</scene>, CYS 38 in the hydrogenase and CYS10 in the cytochrome, are thought to provide the electron transfer pathway between the two proteins (these scenes were created by Jaime Prilusky, David S. Goodsell, and Eran Hodis).

==  Conformational control of the binding of diatomic gases to cytochrome c’ <ref>PMID 25792378 </ref>==

The cytochromes c′ (CYTcp) are found in denitrifying, methanotrophic and photosynthetic bacteria. These proteins are able to form stable adducts with CO and NO but not with O2. The binding of NO to CYTcp currently provides the best structural model for the NO activation mechanism of soluble guanylate cyclase. Ligand binding in CYTcps has been shown to be highly dependent on residues in both the proximal and distal heme pockets. Group 1 CYTcps typically have a phenylalanine residue positioned close to the distal face of heme, while for group 2, this residue is typically leucine. We have structurally, spectroscopically and kinetically characterised the CYTcp from ''Shewanella frigidimarina'' <scene name='69/696899/Cv/2'>(SFCP)</scene>, a protein that has a distal phenylalanine residue and a lysine in the proximal pocket in place of the more common arginine (<font color='red'><b>monomer A is colored in red</b></font>, <span style="color:lime;background-color:black;font-weight:bold;">monomer B in green</span>, and <span style="color:yellow;background-color:black;font-weight:bold;">heme group in yellow</span>). <scene name='69/696899/Cv/3'>Each monomer of the SFCP dimer folds as a 4-alpha-helical bundle</scene> in a similar manner to CYTcps previously characterised. 
* <scene name='69/696899/Cv/4'>Heme group and its environment in as-isolated SFCP</scene>.
* <scene name='69/696899/Cv/5'>Proximal NO complex of SFCP (monomer A)</scene>.
* <scene name='69/696899/Cv/8'>Click here to see the difference between these structures</scene>.
SFCP exhibits biphasic binding kinetics for both NO and CO as a result of the high level of steric hindrance from the aromatic side chain of residue Phe 16. The binding of distal ligands is thus controlled by the conformation of the phenylalanine ring. 
* <scene name='69/696899/Cv/12'>A superposition of the heme environments</scene> of <span style="color:lime;background-color:black;font-weight:bold;">SFCP (in green</span>;[[4ulv]]), <font color='magenta'><b>RCCP (''R. capsulatus''; in magenta</b></font>; [[1cpq]]), <font color='red'><b>RSCP (''R. sphaeroides''; in red</b></font>; [[1gqa]]) and <span style="color:cyan;background-color:black;font-weight:bold;">RGCP (''R. gelatinosus''; in cya)</span>; [[2j8w]]).
* <scene name='69/696899/Cv/14'>Click here to see morph of this scene</scene>.
Only a proximal 5-coordinate NO adduct, confirmed by structural data, is observed with no detectable hexacoordinate distal NO adduct.
</StructureSection>

==3D structures of cytochrome C==

Updated on {{REVISIONDAY2}}-{{MONTHNAME|{{REVISIONMONTH}}}}-{{REVISIONYEAR}}
{{#tree:id=OrganizedByTopic|openlevels=0|

*Cytochrome C

**[[3nwv]], [[3zoo]] – hCyt (mutant) – human<BR />
**[[3zcf]] – hCyt<br />
**[[1j3s]] – hCyt - NMR<BR />
**[[3nbs]], [[3nbt]], [[1crc]], [[1hrc]], [[3o1y]], [[3o20]], [[3wc8]], [[3wui]], [[4rsz]] – hoCyt – horse<BR />
**[[1lc1]], [[1lc2]], [[1m60]], [[1giw]], [[2giw]], [[1akk]], [[2frc]], [[1ocd]] – hoCyt – NMR<BR />
**[[1fi9]], [[1fi7]] - hoCyt + imidazole – NMR<BR />
**[[1u75]] - hoCyt + Cyt peroxidase<BR />
**[[1wej]] – hoCyt + Fab fragment<BR />
**[[3a9f]] – CtCyt C-terminal – ''Chlorobaculum tepidum''<BR />
**[[3cp5]] – Cyt residues 29-152 – ''Rhodothermus marinus''<BR />
**[[2jti]], [[3tyi]] – yCyt (mutant) + Cyt peroxidase – yeast<BR />
**[[2pcb]] - yCyt + Cyt peroxidase<BR />
**[[2gb8]] - yCyt + Cyt peroxidase - NMR<BR />
**[[2jqr]] - yCyt (mutant) + adrenodoxin<BR />
**[[2orl]] - yCyt (mutant) – NMR<BR />
**[[1crg]], [[1crh]], [[1cri]], [[1crj]], [[ 2ycc]] - yCyt<BR />
**[[1ytc]], [[1cie]], [[1cif]], [[1cig]], [[1cih]], [[1csu]], [[1csv]], [[1csw]], [[1csx]], [[1chh]], [[1chi]], [[1chj]], [[1cty]], [[1ctz]] - yCyt (mutant)<br />
**[[1rap]], [[1raq]], [[1ycc]]- yCyt iso-1<BR />
**[[1yic]] – yCyt iso-1 – NMR<BR />
**[[1irv]], [[1irw]], [[1lms]], [[4mu8]], [[4n0k]] – yCyt iso-1 (mutant) <BR />
**[[2hv4]], [[2lir]], [[2lit]], [[2mhm]] - yCyt iso-1 (mutant) - NMR<br />
**[[1fhb]] - yCyt iso-1 (mutant) + CN - NMR<BR />
**[[1nmi]] – yCyt iso-1 + imidazole<BR />
**[[2b0z]], [[2b10]], [[2b11]], [[2b12]], [[1u74]], [[1s6v]], [[2bcn]] – yCyt iso-1 (mutant) + Cyt peroxidase<BR />
**[[2pcc]] – yCyt iso-1 + Cyt peroxidase<BR />
**[[1yea]], [[1yeb]] – yCyt iso-2<BR />
**[[2e84]] – DvCyt – ''Desulfovibrio vulgaris''<BR />
**[[2j7a]] – DvCyt catalytic + electron donor subunits<BR />
**[[2oz1]] – RsuCyt – ''Rhodovulum sulfidophilum''<BR />
**[[1h31]], [[1h32]], [[1h33]] – RsuCyt diheme<br />
**[[2aiu]] – Cyt – mouse<BR />
**[[2fw5]], [[2fwt]] – RsCyt diheme residues 1-139 - ''Rhodobacter sphaeroides''<BR />
**[[1dw0]], [[1dw3]] - RsCyt diheme residues 1-112<BR />
**[[1dw1]], [[1dw2]] - RsCyt diheme residues 1-112 + small molecule<BR />
**[[1ogy]] - RsCyt diheme residues 25-154 + nitrate reductase catalytic subunit<BR />
**[[2a3m]], [[2a3p]] – DdCyt tetraheme membrane-bound subunit - ''Desulfovibrio desulfuricans''<BR />
**[[1h21]] - DdCyt di-heme<BR />
**[[1ofw]], [[1ofy]], [[1duw]], [[19hc]] - DdCyt nine-heme<BR />
**[[1oah]] - DdCyt<BR />
**[[2b4z]] – bCyt – bovine<BR />
**[[1lfm]], [[1i55]], [[3cyt]], [[1i54]], [[1i5t]] -  Cyt – tuna<BR />
**[[1fs7]], [[1fs8]], [[1fs9]] – WsCyt + small molecule – ''Wolinella succinogenes''<BR />
**[[1dxr]] – RvCyt in photosynthetic reaction center – ''Rhodopseudomonas viridis''<BR />
**[[1qdb]] – Cyt – ''Sulfurospirillum deleyianum''<BR />
**[[5cyt]] – Cyt - albacore<br />
**[[2ccy]] – Cyt – ''Phaeospirillum molischianum''<br />
**[[4dy9]] – Cyt – ''Leishmania major''<br />
**[[3u99]] – Cyt diheme – ''Shewanella baltica''<br />
**[[3j2t]] – Cyt + apoptotic protease-activating factor 1 – bovine – Cryo EM<br />

*Cytochrome C’

**[[2xl6]], [[2xld]], [[2xle]], [[2xlo]], [[2xlv]], [[2xlw]] – AxCyt (mutant) + NO – ''Achromobacter xylosoxidans''<BR />
**[[1cgn]], [[1cgo]], [[2ykz]], [[3zqv]], [[2yli]], [[4cda]], [[4cdv]], [[4cdy]], [[4cip]], [[4cjo]], [[4wgy]], [[4wgz]] - AxCyt<BR />
**[[2xm0]], [[2xm4]], [[2xl8]], [[2xlh]], [[2yl0]], [[2yl7]], [[3ztm]] - AxCyt (mutant) <BR /> 
**[[2yl1]], [[2yl3]], [[2ylg]], [[3zqy]], [[3ztz]] - AxCyt (mutant) + CO<br />
**[[2yld]], [[3zwi]] - AxCyt + CO<br />
**[[2xlm]], [[4cjg]] - AxCyt + NO<BR />
**[[2j9b]], [[2j8w]] – Cyt – ''Rubrivivax gelatinosus''<BR />
**[[1gqa]] – RsCyt<BR />
**[[1mqv]], [[1a7v]] – RpCyt – ''Rhodopseudomonas palustris''<BR />
**[[1eky]] – RcCyt]] - ''Rhodobacter capsulatus'' – NMR<BR />
**[[1cpr]], [[1cpq]], [[1rcp]] – RcCyt<BR />
**[[1nbb]] – RcCyt + cyanide<BR />
**[[1e83]], [[1e84]], [[1e85]], [[1e86]] – Cyt - ''Alcaligenes xylosoxidans''<BR />
**[[1jaf]] – Cyt – ''Rhodocyclus gelatinosus''<BR />
**[[1bbh]] – Cyt – ''Allochromatium vinosum''<br />
**[[3vcr]] - CtCyt<br />
**[[3vrc]] – Cyt – ''Thermochromatium tepidum''<br />
**[[4cx9]] - Cyt – ''Shewanella frigidimarina''<br />
**[[4ulv]] - Cyt + NO – ''Shewanella frigidimarina''<br />

*Cytochrome C’’

**[[1oae]], [[1gu2]] – MmCyt – ''Methylophilus methylotrophus''<BR />
**[[1e8e]] – MmCyt - NMR<BR />

*Cytochrome C1

**[[3cx5]], [[3cxh]] – yCyt in complex III<BR />
**[[2ibz]] - yCyt in complex III + inhibitor<BR />
**[[1kyo]] - yCyt in Bc1 complex<BR />
**[[1kb9]] – yCyt in Bc1 complex residues 17-368<BR />
**[[1ezv]] - yCyt in Bc1 complex + antibody FV fragment<BR />
**[[3h1h]], [[1bcc]] - cCyt in Bc1 complex – chicken<BR />
**[[3h1i]], [[2bcc]], [[3bcc]] - cCyt in Bc1 complex + inhibitor<BR />
**[[2qjk]], [[2qjp]], [[2qjy]] – RsCyt in Bc1 complex + inhibitor<BR /> 
**[[2fyn]] - RsCyt in Bc1 complex (mutant) <BR />
**[[1l0n]], [[1be3]], [[1bgy]], [[1qcr]] – bCyt in Bc1 complex<BR />
**[[2fyu]] - bCyt in Bc1 complex (mutant) + inhibitor<BR /> 
**[[1sqp]], [[1sqq]], [[1sqv]], [[1sqx]], [[2a06]], [[1sqb]], [[1pp9]], [[1ppj]], [[1ntk]], [[1ntm]], [[1p84]], [[1l0l]] - bCyt in Bc1 complex + inhibitor<BR />
**[[1ntz]], [[1nu1]] - bCyt in Bc1 complex + substrate<BR />
**[[1zrt]] - RcCyt in Bc1 complex + inhibitor<br />
**[[2yiu]] - PdCyt in Bc1 complex – ''Paracoccus denitrificans'' 

*Cytochrome C2

**[[1c2r]] - RcCyt<BR />
**[[1vyd]] – RcCyt (mutant) <BR />
**[[1c2n]] – RcCyt - NMR<BR />
**[[1l9b]], [[1l9j]] – RsCyt in photosynthetic reaction center<BR />
**[[2cxb]], [[1cxc]], [[1cxa]] - RsCyt<BR />
**[[1jdl]] – Cyt – ''Rhodospirillum centenum''<BR />
**[[2c2c]], [[3c2c]] – Cyt – ''Rhodospirillum rubrum''<BR />
**[[1i8o]], [[1hh7]], [[1fj0]], [[1i8p]] – RpCyt<BR />
**[[1hro]] – Cyt – ''Rhodopila globiformis''<BR />
**[[1cot]] – PdCyt - ''Paracoccus denitrificans''<BR />
**[[1cry]] - RvCyt<br />
**[[1co6]], [[1io3]] – BvCyt - ''Blastochloris viridis''

*Cytochrome C3

**[[2ksu]], [[1up9]], [[1upd]], [[1gmb]], [[1gm4]], [[1i77]], [[3cyr]] – DdCyt<BR /> 
**[[2kmy]] – DdCyt – NMR<BR />
**[[2k3v]] – Cyt – ''Shewanella frigidimarina''<BR />
**[[1m1p]], [[1m1r]], [[1m1q]] - SoCyt tetraheme – ''Shewanella oneidensis''<BR />
**[[3pmq]] - SoCyt decaheme<br />
**[[1it1]] – DvCyt<br />
**[[2bpn]] – DvCyt fragment - NMR<br />
**[[1j0o]], [[2cth]], [[2cdv]] - DvCyt tetraheme<BR />
**[[2z47]], [[2yyw]], [[2yyx]], [[2yxc]], [[2ffn]], [[2ewi]], [[2ewk]], [[2ewu]], [[1wr5]], [[1j0p]], [[1mdv]], [[2cym]] – DvCyt tetraheme (mutant) <BR />
**[[1gx7]] – DvCyt + hydrogenase<BR />
**[[1gyo]], [[1wad]], [[1qn0]], [[1qn1]] - DgCyt di-tetraheme – ''Desulfovibrio gigas''<BR />
**[[1z1n]] - DgCyt sixteen heme<br />
**[[2bq4]], [[3cao]], [[3car]] – Cyt – ''Desulfovibrio africanus''<BR />
**[[1w7o]] - Cyt – ''Desulfomicrobium baculatus''<BR />
**[[1aqe]] – DnCyt (mutant) – ''Desulfomicrobium norvegicum''<br />
**[[1czj]], [[2cy3]] - DnCyt<br />
**[[1a2i]] - DvCyt<br />
**[[2ldo]] – GsCyt residues 21-91 – ''Geobacter sulfurreducens'' - NMR<br />
**[[2izz]] - GsCyt residues 21-91 (mutant) – NMR<br />
**[[3ov0]] – GsCyt residues 26-343 dodedcaheme<br />
**[[3ouq]] - GsCyt residues 26-186 hexaheme<br />
**[[3oue]] - GsCyt residues 186-343 hexaheme

*Cytochrome C4

**[[1m6z]], [[1m70]], [[1etp]] – PsCyt – ''Pseudomonas stutzeri''<BR />
**[[1h1o]] – Cyt - ''Acidithiobacillus ferrooxidans''

*Cytochrome C5

**[[1cc5]] – Cyt – ''Azotobacter vinelandii''

*Cytochrome C6

**[[3ph2]] – PlCyt (mutant) – ''Phormidium laminosum''<BR />
**[[3dr0]], [[4eic]], [[4eie]] – SyCyt – ''Synechococcus''<BR />
**[[4eid]], [[4eif]] – SyCyt (mutant)<br />
**[[3dmi]] – Cyt – ''Phaeodactylum tricornutum''<BR />
**[[2zbo]] – Cyt – ''Hizikia fusiformis''<BR />
**[[2v07]], [[2dge]] – AtCyt residues 71-175 – ''Arabidopsis thaliana''<BR />
**[[2ce0]], [[2ce1]] - AtCyt residues 71-175 (mutant) <BR />
**[[2v08]] – PlCyt <BR />
**[[1ls9]] – Cyt – ''Cladophora glomerata''<BR />
**[[1kib]], [[1f1f ]] – AmCyt – ''Arthrospira maxima''<BR />
**[[1gdv]] – Cyt – ''Porphyra yezoensis''<BR />
**[[1a2s]], [[1ced]] – MbCyt – ''Monoraphidium braunii'' – NMR<BR />
**[[1ctj]] - MbCyt<BR />
**[[1c6s]] – Cyt – ''Cyanobacterium synechococcus'' - NMR<BR />
**[[1c6o]], [[1c6r]] – Cyt – ''Scenedesmus obliquus''<br />
**[[1ccr]] – Cyt - rice<br />
**[[4gyd]] – noCyt – nostoc<br />
**[[4h0j]], [[4h0k]] – noCyt (mutant) <br />

*Cytochrome C7

**[[3h33]], [[3h34]], [[3h4n]], [[3bxu]] – GsCyt <BR />
**[[1lm2]], [[1l3o]], [[1kwj]], [[1f22]], [[1ehj]] – DaCyt – ''Deulfurmonas acetoxidans'' – NMR<BR />
**[[1hh5]] - DaCyt<br />
**[[3sel]], [[3sj0]], [[3sj1]], [[3sj4]] – Cyt (mutant) – ''Geobascter desulfurreducens''<br />

*Cytochrome C549

**[[1f1c]] – AmCyt<BR />
**[[1e29]] - SyCyt

*Cytochrome C550

**[[3wu2]], [[4v82]], [[3kzi]], [[3a0b]], [[3a0h]], [[4v62]], [[1izl]], [[5ws6]], [[5ws5]], [[5v2c]], [[5gti]], [[5gth]], [[5b66]], [[5b5e]], [[4ub8]], [[4ub6]], [[4il6]] – Cyt in photosystem II – ''Thermosynechococcus vulcanus''<BR />
**[[2axt]], [[1w5c]], [[1s5l]], [[5h2f]], [[5tis]], [[5mx2]], [[5kai]], [[5kaf]], [[5e7c]], [[5e79]], [[4tnk]], [[4tnj]], [[4tni]], [[4tnh]], [[4rvy]], [[4pj0]], [[4pbu]], [[4ixr]], [[4ixq]], [[4fby]] - TeCyt in photosystem II – ''Thermosynechococcus elongatus''<BR />
**[[2bgv]] – PvCyt – ''Paracoccus versutus''<BR />
**[[2bh4]], [[2bh5]] – PvCyt (mutant) <BR />
**[[1mz4]] – TeCyt<BR />
**[[155c]] - PdCyt

*Cytochrome C551

**[[2zon]] – AxCyt + nitrite reductase<BR />
**[[2gc7]], [[2gc4]], [[2mta]] – PdCyt + methylamine dehydrogenase + amicyanin<BR />
**[[1cch]], [[1cor]] – PsCyt - NMR<BR /> 
**[[1gks]] – Cyt – ''Ectothiorhodospira halophila'' - NMR<BR />
**[[1new]] – DaCyt triheme]- NMR<BR />
**[[2exv]] – PaCyt (mutant) – ''Pseudomonas aeruginosa''<BR />
**[[351c]], [[451c]] - PaCyt<BR />
**[[2pac]] – PaCyt - NMR<BR />
**[[1dvv]] - PaCyt (mutant) – NMR<BR />
**[[1fi3]], [[2i8f]] - PsCyt (mutant) – NMR<br />
**[[5xec]], [[5xed]] – Cyt551/Cyt552 – ''Hydrogenobacter thermophilus''<br />

*Cytochrome C552 [[Nitrite reductase]]

*Cytochrome C553

**[[1b7v]], [[1c75]] – BpCyt - ''Bacillus pasteuri''<BR />
**[[1k3h]], [[1k3g]] – BpCyt – NMR<BR />
**[[1e08]] – DdCyt + hydrogenase - NMR<BR />
**[[1n9c]] – Cyt – ''Sporosarcina pasteurii''<BR />
**[[1c53]] - DvCyt<BR />
**[[1dvh]] - DvCyt - NMR<br />
**[[2dvh]] - DvCyt (mutant) - NMR<BR />
**[[1dwl]] – DvCyt + ferredoxin I – NMR<BR />
**[[1cyi]], [[1cyj]] – Cyt – ''Chlamydomonas reinhardtii''

*Cytochrome C554

**[[2zzs]] – Cyt – ''Vibrio parahaemolyticus''<BR />
**[[1ft5]], [[1ft6]], [[1bvb]] – Cyt – ''Nitrosomonas europaea''

*Cytochrome C555

**[[2zxy]] – Cyt – ''Aquifex aeolicus''<BR />
**[[2yk3]] – Cyt – ''Crithidia fasciculate''<br />
**[[4j20]] – CtCyt (mutant)<br />

* Cytochrome C557

**[[1foc]] – TtCyt – ''Thermus thermophilus''<br />

*Cytochrome C556

**[[1s05]] – RpCyt - NMR<BR />

*Cytochrome C558

**[[2x5u]], [[2x5v]] – BvCyt in photosynthetic reaction center – ''Blastochloris viridis'' – Laue<BR />
**[[2wjm]], [[2wjn]], [[3g7f]], [[3d38]], [[2jbl]], [[2i5n]], [[1vrn]], [[1r2c]] - BvCyt in photosynthetic reaction center 

*Cytochrome C562

**[[3qvz]] – EcCyt + Cu + Zn 

*Cytochrome C NAPB

**[[3ml1]], [[3o5a]] – Cyt + nitrate reductase catalytic subunit – ''Ralstonia eutropha''<br />
**[[1jni]] – Cyt small subunit – ''Haemophilus influenzae''

*Cytochrome CL

**[[2d0w]] – Cyt – ''Hyphomicrobium denitrificans''<BR />
**[[2c8s]] – MeCyt – ''Methylobacterium extorquens''<br />
**[[1mg2]], [[1mg3]] – PdCyt + methylamine hydrogenase + amicyanin<br />

*Cytochrome CC3

**[[2cvc]], [[1gws]], [[1h29]] – DvCyt

*Cytochrome CD1

**[[1gq1]], [[1h9x]], [[1h9y]], [[1hcm]], [[1qks]] – Cyt – ''Paracoccus pantotrophus''<BR />
**[[1gjq ]]– PaCyt<BR /> 
**[[1dy7]] – PaCyt + CO<BR />
**[[1e2r]] – PdCyt + CN 

*Cytochrome CH

**[[1qn2]] – MeCyt 

*Cytochrome CB562

**[[3qvy]], [[3qw0]], [[3qw1]] – EcCyt + Zn<br />
**[[3c62]], [[3c63]], [[3iq5]], [[3iq6]], [[3l1m]], [[3m15]], [[3nmi]], [[3nmk]] - EcCyt (mutant) + Zn<br />
**[[3de8]], [[3m79]] - EcCyt (mutant) + Zn + Cu<br />
**[[3de9]], [[3nmj]] - EcCyt (mutant) + Zn + Ni
}}
== References ==

<references/>

[[Category:Topic Page]]