View source for Cytochrome C1

{{Short description|Protein encoded by the CYC1 gene}}
{{Infobox protein
| name = Cytochrome C1
| AltNames =Complex III subunit 4, Ubiquinol-cytochrome-c reductase complex cytochrome c1 subunit
| image = 
| width = 
| caption = 
| Symbol = CYC1
| AltSymbols = UQCR4, MC3DN6
| IUPHAR_id = 
| ATC_prefix = 
| ATC_suffix = 
| ATC_supplemental = 
| CAS_number = 
| CAS_supplemental = 
| DrugBank = 
| EntrezGene = 1537
| HGNCid = 2579
| OMIM = 123980
| PDB = 
| RefSeq = NM_001916.4
| UniProt = P08574
| ECnumber = 
| Chromosome = 8
| Arm = 24
| Band = 3
| LocusSupplementaryData = 
}}

'''Cytochrome C1''' (also known as '''Complex III subunit 4''') is a protein encoded by the ''[[CYC1]]'' gene. Cytochrome is a [[heme]]-containing subunit of the [[Cytochrome bc1 complex|cytochrome b-c1 complex]], which accepts electrons from [[Rieske protein]] and transfers electrons to [[cytochrome c]] in the [[mitochondrial respiratory chain]].<ref>{{Cite web|url=https://www.uniprot.org/uniprot/P08574|title=CYC1 - Cytochrome c1, heme protein, mitochondrial precursor - Homo sapiens (Human) - CYC1 gene & protein|website=www.uniprot.org|access-date=2016-07-29}}</ref> It is formed in the [[cytosol]] and [[protein targeting|targeted]] to the [[mitochondrial intermembrane space]]. Cytochrome c1 belongs to the [[cytochrome c family]] of proteins.

== Function ==
Cytochrome C1 plays a role in the [[electron transfer]] during [[oxidative phosphorylation]]. As an [[Iron–sulfur protein|iron-sulfur protein]] approaches the b-c1 complex, it accepts an electron from the [[cytochrome b]] subunit, then undergoes a [[conformational change]] to attach to cytochrome c1. There, the electron carried by the iron-sulfur protein is transferred to the heme carried by cytochrome c1. This electron is then transferred to a heme carried by cytochrome c. This creates a [[Redox|reduced species]] of cytochrome c, which separates from the b-c1 complex and moves to the last enzyme in the electron transport chain, [[cytochrome c oxidase]] (Complex IV).<ref>{{cite journal | vauthors = Kokhan O, Wraight CA, Tajkhorshid E | title = The binding interface of cytochrome c and cytochrome c₁ in the bc₁ complex: rationalizing the role of key residues | journal = Biophysical Journal | volume = 99 | issue = 8 | pages = 2647–56 | date = October 2010 | pmid = 20959106 | pmc = 2955499 | doi = 10.1016/j.bpj.2010.08.042 }}</ref>

== Species ==
''CYC1'' is a human gene that is [[Conserved sequence|conserved]] in [[Common chimpanzee|chimpanzee]], [[Rhesus monkey]], dog, cow, mouse, rat, [[zebrafish]], [[Drosophila melanogaster|fruit fly]], mosquito, [[Caenorhabditis elegans|''C. elegans'']], ''[[S. cerevisiae]],'' ''[[K.lactis|K. lactis]]'', ''[[E. gossypii]]'', ''[[S. pombe]]'', ''[[N. crassa]]'', ''[[A. thaliana]]'', rice, and frog.<ref>{{Cite web|url=https://www.ncbi.nlm.nih.gov/gene/1537|title=CYC1 cytochrome c1 [Homo sapiens (human)]|last=|first=|date=|website=National Center for Biotechnology Information|publisher=U.S. National Library of Medicine|access-date=2016-07-29}}</ref> There are [[orthologs]] of CYC1 in 137 known organisms.<ref>{{Cite web|url=https://www.ncbi.nlm.nih.gov/gene/?Term=ortholog_gene_1537%5Bgroup%5D|title=ortholog_gene_1537[group]|last=|first=|date=|website=National Center for Biotechnology Information|publisher=U.S. National Library of Medicine|access-date=2016-07-29}}</ref>

In its structure and function, the cytochrome b-c1 complex bears extensive analogy to the [[cytochrome b6f complex]] of [[chloroplast]]s and [[cyanobacteria]]; cytochrome c1 plays an analogous role to [[cytochrome f]], despite their different structures.<ref name="pmid7631417">{{cite journal | vauthors = Prince RC, George GN | title = Cytochrome f revealed | journal = Trends in Biochemical Sciences | volume = 20 | issue = 6 | pages = 217–8 | date = June 1995 | pmid = 7631417 | doi = 10.1016/S0968-0004(00)89018-0 }}</ref>

== Clinical relevance ==
Mutations in the ''CYC1'' gene are associated with mitochondrial complex III deficiency nuclear type 6. The disease symptoms include early childhood onset of severe [[lactic acidosis]] and [[ketoacidosis]], usually in response to infection. Insulin-responsive [[hyperglycemia]] is also present, but [[Psychomotor learning|psychomotor development]] appears normal. Mutation of ''CYC1'' was observed to cause instability in the cytochrome b-c1 complex, which decreased its ability to create energy through oxidative phosphorylation.<ref>{{OMIM|123980|Cytochrome C!; CYC1}}</ref> Mitochondrial complex III deficiency nuclear type 6 is [[autosomal recessive]].<ref>{{cite web | url = http://www.omim.org/geneMap/8/540?start=-3&limit=10&highlight=540 | title = OMIM Gene Map | website = Online Mendelian Inheritance in Man|publisher=Johns Hopkins University.|access-date=2016-07-29}}</ref>

== References ==
{{Reflist}}

== External links ==
* {{MeshName|Cytochrome+c1}}

{{InterPro content|IPR002326}}
{{Electron transport chain}}

[[Category:Transmembrane proteins]]
[[Category:Cellular respiration]]