Electron carrier protein. The oxidized form of the cytochrome c heme group can accept an electron from the heme group of the cytochrome c1 subunit of ubiquinol-cytochrome c oxidoreductase. Cytochrome c then transfers this electron to the dinuclear copper A center (CU(A)) of the COX2 subunit of cytochrome oxidase, the final protein carrier in the mitochondrial electron-transport chain. Isoform 2 (CYC7) is the predominant cytochrome c under anaerobic/hypoxic conditions. Binds 1 heme c group covalently per subunit. By low oxygen levels (hypoxia) at the level of transcription. Not expressed until the oxygen concentration is below 0.5 uM O(2). Present with 1310 molecules/cell in log phase SD medium. Belongs to the cytochrome c family. Life shuttle - Issue 76 of November 2006