ELECTROPHORETIC AND DYNAMIC LIGHT-SCATTERING STUDY OF THE INTERACTIONOF CYTOCHROME-C WITH DIMYRISTOYL PHOSPHATIDYLGLYCEROL, DIMYRISTOYLPHOSPHATIDYLCHOLINE, AND INTRAMEMBRANOUSLY MIXED LIPOSOMES

The binding of cytochrome c to liposomes was studied by electrophoreti c light scattering and dynamic light scattering measurements. Pure dim yristoylphosphatidylglycerol (DMPG) and dimyristoylphosphatidylcholine (DMPC), as well as intramembranously mixed DMPC-DMPG liposomal disper sions were investigated, Thus, the charge density of the liposomes was varied within a broad range, Because of adsorption of the protein ont o the anionic liposome types, the electrophoretic mobility of the DMPG -containing liposomal dispersions was significantly reduced, These res ults confirmed the generally accepted model of interaction between cyt ochrome c and phospholipids, which assumes the adsorption process to b e electrostatically controlled; however, the experimentally observed c harge reinversion phenomenon indicated that some other type(s) of inte raction(s) between phospholipids and cytochrome c seems to control the overall binding process as well. From dynamic light scattering measur ements it was found that cytochrome c addition induced DMPG liposome a ggregation, From the dependence of the aggregation kinetics on the cyt ochrome c-to-phospholipid ratio, it was deduced that charge neutraliza tion was accompanied by bridging, especially at lower protein-to-DMPG ratios. (C) 1997 Academic Press.