Cytochrome bc1 complex

Template:STRUCTURE 1bcc Cytochrome bc1 (Cbc1) functions as the central pump which transfers protons across the cell membrane. The protons are used to power the rotation of ATP synthase. Cbc1 binds ubiquinol which carries hydrogen atoms. Cbc1 separates the protons and the electrons. The protons are released in the inner side of the membrane for use by ATP synthase and the electrons are transferred to cytochrome c or to the outer side of the membrane. Cbc1 is a dimeric protein composed of 11 proteins and cofactors which include heme and iron-sulfur cluster. Plants use cytochrome b6f in the same manner binding plastoquinol as a hydrogen carrier. Stigmatellin is an inhibitor of the Cbc1 electron transfer by binding to its quinone oxidation site. Antimycin inhibits Cbc1 by binding to its quinone reduction site.

Cytochrome bc1 in complex III of the mitochondrial electron transport chain.

3D structures of cytochrome bc13D structures of cytochrome bc1

1bcc – cCbc1 + ubiquinone-10 + heme + Fe2S2 – chicken
3bcc, 3h1i – cCbc1 + stigmatellin + antimycin + heme + Fe2S2
2bcc - cCbc1 + ubiquinone-10 + stigmatellin + heme + Fe2S2
3h1h - cCbc1 + ubiquinone-10 + heme + Fe2S2
1qcr – bCbc1 (Cα atoms) + heme - bovine
1bgy, 1be3 - bCbc1 + heme + Fe2S2
1pp9, 2a06 - bCbc1 + ubiquinone-10 + stigmatellin + heme + Fe2S2
1ppj - bCbc1 + stigmatellin + antimycin + heme + Fe2S2

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Michal Harel, Alexander Berchansky, Karl Oberholser, Jaime Prilusky, Joel L. Sussman