[Rapid transmembrane migration of phosphatidylcholine under the influence of cytochrome P-450]

The phosphatidylcholine exchange protein and bee venom phospholipase A2 were used to estimate the phosphatidylcholine accessibility in proteoliposome-containing cytochrome P-450. Without cytochrome P-450 phosphatidylcholine was only partly accessible for the both membrane probes. Incorporation of cytochrome P-450 into the liposomes resulted in a complete accessibility of phosphatidylcholine for the phosphatidylcholine exchange protein and phospholipase A2. On the other hand, phosphatidylcholine was only partly available for the membrane probes in cytochrome b5 containing proteoliposomes. It was concluded that cytochrome P-450 induces rapid transmembrane translocation of phosphatidylcholine with tau 1/2 less than 20 min. It is proposed that cytochrome P-450 may be responsible for rapid flip-flop of phosphatidylcholine in rat liver microsomes.