Cytochrome c1, heme protein, mitochondrial (CYC1)

Cytochrome c1 is a 30-kDa membrane-bound heme protein that serves as a catalytic subunit of mitochondrial complex III (cytochrome bc1 complex). It facilitates the transfer of electrons from the Rieske iron-sulfur protein to cytochrome c during oxidative phosphorylation. Cytochrome c1 is anchored in the inner mitochondrial membrane, with its functional domain projecting into the intermembrane space. Dysfunction of cytochrome c1 impairs electron flow in the respiratory chain, leading to decreased ATP production and increased reactive oxygen species. Mutations in CYC1 are linked to rare mitochondrial diseases. Cytochrome c1 arose evolutionarily from a collapse of a di-heme cytochrome c4 ancestor, and maintains a mono-heme structure essential for its role in electron transfer. It is a highly conserved protein across eukaryotes, and bears sequence homology indicating its functional and evolutionary significance in cellular respiration.

Other names

CYC1Cytochrome c1Cytochrome bc1 complex subunit 3Complex III subunit 3Mitochondrial cytochrome c1

Inhibitors of cytochrome bc1 complex (complex III) prevent electron transfer between ubiquinol and cytochrome c, collapsing the proton gradient and impairing ATP synthesis, leading to cell death or dysfunction