STUDY ON THE TRANSLOCATION OF MITOCHONDRIAL PRECURSOR PROTEIN ACROSS MODEL MEMBRANES——THE INTERACTION BETWEEN Candida krusei APOCYTOCHROME c AND NON-BILAYER LIPID PHOSPHATIDYLETHANOLAMINE(PE)

The import rate of Candida krusei apocytochrome c across three types of liposomes:50%PS-50%PC(a),50%PS-12.5%PE-37.5%PC(b)and 50%PS-25%PE-25%PC(c)follows this order:c>b>a.It may indicate that the import rate increases with increasing content of non-bilayer lipid PE invesicles despite the same binding ability of apocytochrome c to these liposomes.The lipid fluidity ofliposomes(a),(b)and(c)measured before or following insertion of apocytochrome c by means of a flu-orescent probe,9-(9-anthroyloxy)stearic acid,decreases in the order of a>b>c.Using N-(7-nitro-2-1,3-benzoxadiazo1-4-yl)dioleoyl ethanolamine(NBD-DOPE),an induction of hexagonal phase transi-tion can be detected in the case of liposomes(b)or(c).It is suggested that local formation of non-bilayer lipid structure could facilitate the translocation of apocytochrome c across the membranes.