Cytochrome C1

Cytochrome C1 is formed in the cytosol and targeted to the mitochondrial intermembrane space. It is one of the constituents of complex III, which forms the third proton pump in the mitochondrial electron transport chain.

Cytochrome c1 is a subunit of the electron transport chain protein Ubiquinol Cytochrome c Reductase (UQCR, Complex III or Cytochrome bc1 complex), which consists of the products of one mitochondrially encoded gene, MTCYTB (mitochondrial cytochrome b) and ten nuclear genes: UQCRC1, UQCRC2, Cytochrome c1, UQCRFS1 (Rieske protein), UQCRB, UQCRQ ("11kDa protein"), UQCRH (cyt c1 Hinge protein), Rieske Protein presequence, "cyt. c1 associated protein", and UQCR ("Rieske-associated protein").

Ubiquinol:ferricytochrome c oxidoreductase is found in mitochondria, photosynthetic bacteria and other prokaryotes. The general function of the complex is electron transfer between two mobile redox carriers, ubiquinol and cytochrome c; the electron transfer is coupled with proton translocation across the membrane, thus generating proton-motive force in the form of an electrochemical potential that can drive ATP synthesis. In its structure and functions, the cytochrome bc1 complex bears extensive analogy to the cytochrome b6f complex of chloroplasts and cyanobacteria; cyt c1 plays an analogous role to cytochrome f, in spite of their different structures.