Electrophoretic and dynamic light scattering study of the interaction of cytochrome c with dimyristoyl phosphatidylglycerol, dimyristoylphosphatidylcholine, and intramembranously mixed liposomes

The binding of cytochrome c to liposomes was studied by electrophoretic light scattering and dynamic light scattering measurements. Pure dimyristoylphosphatidylglycerol (DMPG) and dimyristoylphosphatidylcholine (DMPC), as well as intramembranously mixed DMPC-DMPG liposomal dispersions were investigated, Thus, the charge density of the liposomes was varied within a broad range, Because of adsorption of the protein onto the anionic liposome types, the electrophoretic mobility of the DMPG-containing liposomal dispersions was significantly reduced, These results confirmed the generally accepted model of interaction between cytochrome c and phospholipids, which assumes the adsorption process to be electrostatically controlled; however, the experimentally observed charge reinversion phenomenon indicated that some other type(s) of interaction(s) between phospholipids and cytochrome c seems to control the overall binding process as well. From dynamic light scattering measurements it was found that cytochrome c addition induced DMPG liposome aggregation, From the dependence of the aggregation kinetics on the cytochrome c-to-phospholipid ratio, it was deduced that charge neutralization was accompanied by bridging, especially at lower protein-to-DMPG ratios. (C) 1997 Academic Press.