Coexistence of Native-Like and Non-Native Misfolded Ferricytochrome C on the Surfac of Cardiolipin Containing Liposomes

Abstract

Cytochrome c, in spite of adopting a rather rigid structure around its prosthetic heme group, is rather diverse with regard to its function and structural variability. On the surface of the inner membrane of mitochondria it serves as an electron transfer carrier. However, at conditions which have not yet been unambiguously identified, cytochrome c can adopt a variety of non-native conformations, some of which exhibit peroxidase activity. Cardiolipin-containing liposomes have served as ideal model system to investigate the various modes of interaction between cytochrome c and the inner mitochrondrial membrane. We probed the binding of horse heart ferricytochrome c to liposomes formed with 20% tetraoleoyl cardiolipin (TOCL) and 80% dioleoyl-sn-glycero-3-phosphocholine (DOPC) as a function of lipid/protein ratio by fluorescence and visible circular dichroism spectroscopy. The obtained binding isotherms suggest that they reflect reversible binding processes, which excludes the possibility of significant prote...