Cytochrome b

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Mitochondrial cytochrome bc1 complex
Identifiers
Symbol	Cytochrom_B_N
Pfam	PF00033
InterPro	IPR005797
PROSITE	PDOC00171
SCOP	3bcc
TCDB	3.D.3
OPM family	3
OPM protein	1bcc
Available PDB structures: 1bccC:10-205 2e74A:10-205 1l0lC:9-204 1ntkC:9-204 1ntmC:9-204 1ntzC:9-204 1sqqC:9-204 1l0nC:9-204 1sqxC:9-204 1nu1C:9-204 1sqvC:9-204 1sqbC:9-204 1be3C:9-204 1sqpC:9-204 1kb9C:8-205 1p84C:8-205 1kyoC:8-205 1q90B:9-210 1vf5A:9-210 2d2cN:9-210

Cytochrome b/b6 is main subunit of transmembrane cytochrome bc1 and b6f complexes.

In the mitochondrion of eukaryotes and in aerobic prokaryotes, cytochrome b is a component of respiratory chain complex III (EC 1.10.2.2) - also known as the bc1 complex or ubiquinol-cytochrome c reductase. In plant chloroplasts and cyanobacteria, there is an analogous protein, cytochrome b6, a component of the plastoquinone-plastocyanin reductase (EC 1.10.99.1), also known as the b6f complex. These complexes are involved in electron transport and the generation of ATP and thus play a vital role in the cell.

Cytochrome b/b6^[1]^[2] is an integral membrane protein of approximately 400 amino acid residues that probably has 8 transmembrane segments. In plants and cyanobacteria, cytochrome b6 consists of two subunits encoded by the petB and petD genes. Cytochrome b/b6 non-covalently binds two heme groups, known as b562 and b566. Four conserved histidine residues are postulated to be the ligands of the iron atoms of these two heme groups.

[edit] References

^ Howell N (1989). "Evolutionary conservation of protein regions in the protonmotive cytochrome b and their possible roles in redox catalysis". J. Mol. Evol. 29 (2): 157–169. doi:10.1007/BF02100114. PMID 2509716.
^ Esposti MD, Crimi M, Ghelli A, Patarnello T, Meyer A, De Vries S (1993). "Mitochondrial cytochrome b: evolution and structure of the protein". Biochim. Biophys. Acta 1143 (3): 243–271. doi:10.1016/0005-2728(93)90197-N. PMID 8329437.