Apocytochrome c

The cytochrome c import pathway differs markedly from the general route taken by the majority of other imported proteins, which is characterized by the import involvement of namely, surface receptors, the general insertion protein (GIP), contact sites and by the requirement of a membrane potential (AO). Unique features of both the cytoehrome c precursor (apocytoehrome c) and of the mechanism that transports it into mitochondria, have contributed to the evolution of a distinct import pathway that is not shared by any other mitochondrial protein analysed thus far. The cytoehrome c pathway is particularly unique because i) apocytochrome c appears to have spontaneous membrane insertion-activity; ii) cytochrome cheme lyase seems to act as a specific binding site in lieu of a surface receptor and; iii) covalent heme addition and the associated refolding of the polypeptide appears to provide the free energy for the translocation of the cytochrome c polypeptide across the outer mitochondrial membrane.