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Main subunit of cytochrome c oxidase

Cytochrome C and Quinol oxidase polypeptide I
Symbol COX1
Pfam PF00115
InterPro IPR000883
SCOP 1occ
TCDB 3.D.4
OPM family 4
OPM protein 1v55
Available PDB structures:

2occN:5-461 1ocrN:5-461 1v54A:5-461 1occA:5-461 1v55A:5-461 1ocoN:5-461 1oczN:5-461 1m57G:19-504 1m56A:19-504 1qleA:21-496 1ehkA:218-309 1fftA:47-505 1xmeA:18-108

Cytochrome C and Quinol oxidase polypeptide I is main subunit of cytochrome c oxidase complex.

Cytochrome c oxidase (EC is a key enzyme in aerobic metabolism. Proton pumping heme-copper oxidases represent the terminal, energy-transfer enzymes of respiratory chains in prokaryotes and eukaryotes. The CuB-heme a3 (or heme o) binuclear centre, associated with the largest subunit I of cytochrome c and ubiquinol oxidases (EC 1.10.3), is directly involved in the coupling between dioxygen reduction and proton pumping[1][2]. Some terminal oxidases generate a transmembrane proton gradient across the plasma membrane (prokaryotes) or the mitochondrial inner membrane (eukaryotes).

The enzyme complex consists of 3-4 subunits (prokaryotes) up to 13 polypeptides (mammals) of which only the catalytic subunit (equivalent to mammalian subunit I (CO I)) is found in all heme-copper respiratory oxidases. The presence of a bimetallic centre (formed by a high-spin heme and copper B) as well as a low-spin heme, both ligated to six conserved histidine residues near the outer side of four transmembrane spans within CO I is common to all family members[3][4][5]. In contrast to eukaryotes the respiratory chain of prokaryotes is branched to multiple terminal oxidases. The enzyme complexes vary in heme and copper composition, substrate type and substrate affinity. The different respiratory oxidases allow the cells to customize their respiratory systems according to a variety of environmental growth conditions[1].

It has been shown that eubacterial quinol oxidase was derived from cytochrome c oxidase in Gram-positive bacteria and that archaebacterial quinol oxidase has an independent origin. A considerable amount of evidence suggests that proteobacteria (Purple bacteria) acquired quinol oxidase through a lateral gene transfer from Gram-positive bacteria[1].

A related nitric oxide reductase (EC exists in denitrifying species of archae and eubacteria and is a heterodimer of cytochromes b and c. Phenazine methosulphate can act as acceptor.



  1. ^ a b c Rumbley J, Gennis RB, Garcia-Horsman JA, Barquera B, Ma J (1994). "The superfamily of heme-copper respiratory oxidases". J. Bacteriol. 176 (18): 5587-5600. PMID 8083153.
  2. ^ Glaser P, Villani G, Papa S, Capitanio N (1994). "The proton pump of heme-copper oxidases". Cell Biol. Int. 18 (5): 345-355. PMID 8049679.
  3. ^ Saraste M, Castresana J, Higgins DG, Lubben M (1994). "Evolution of cytochrome oxidase, an enzyme older than atmospheric oxygen". EMBO J. 13 (11): 2516-2525. PMID 8013452.
  4. ^ Capaldi RA, Malatesta F, Darley-Usmar VM (1983). "Structure of cytochrome c oxidase". Biochim. Biophys. Acta 726 (2). PMID 6307356.
  5. ^ Saraste M, Holm L, Wikstrom M (1987). "Structural models of the redox centres in cytochrome oxidase". EMBO J. 6 (9): 2819-2823. PMID 2824194.


  • Cytochrome c oxidase cbb3-type, subunit I IPR004677
  • Cytochrome o ubiquinol oxidase, subunit I IPR014207
  • Cytochrome aa3 quinol oxidase, subunit I IPR014233
  • Cytochrome c oxidase, subunit I bacterial type IPR014241

Human proteins containing this domain



  • [1]. The whole structure of the 13-subunit oxidized cytochrome c oxidase at 2.8 A. Tsukihara T, Aoyama H, Yamashita E, Tomizaki T,

Yamaguchi H, Shinzawa-Itoh K, Nakashima R, Yaono R, Yoshikawa S; Science 1996;272:1136-1144. PubMed

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Main_subunit_of_cytochrome_c_oxidase". A list of authors is available in Wikipedia.
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