Phosphatidylcholine exchange protein catalyzes the net transfer of phosphatidylcholine to model membranes.
2-Stearoyl spin-labeled phosphatidylcholine (PC*) has been introduced into the phosphatidylcholine exchange protein from bovine liver and its electron spin resonance (ESR) spectrum determined. The spin-labeled group in the PC*- exchange protein complex was strongly immobilized. Addition of sodium deoxycholate micelles released PC* from its binding site, producing a mobile signal. This was also observed when micelles of lysophosphatidylcholine and vesicles of phosphatidic acid were added, indicating that the exchange protein can insert its endogenous PC* into interfaces devoid of phosphatidylcholine. ESR spectroscopy was used to measure transfer of PC* from spin-labeled "donor" vesicles to unlabeled "acceptor" vesicles as described by Machida & Ohnishi [Machida, K., & Ohnishi, S. (1978) Biochim. Biophys. Acta 507, 156-164]. The donor vesicles consisted of PC* and phosphatidic acid (75:25 mol%) and the acceptor vesicles of phosphatidylethanolamine and phosphatidic acid (81:19 mol%). Addition of exchange protein catalyzed a net transfer of PC* from donor to acceptor vesicles. This transfer proceeded until the acceptor vesicles contained approximately 2 mol% of PC*. A spontaneous transfer of PC* was not observed. As for the mode of action, it appears that the exchange protein, after insertion of its endogenous PC* into the acceptor, leaves the interface without a bound phospholipid molecule yet continues to shuttle PC* from donor to acceptor.
D000727:Androgen-Binding Protein; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002417:Cattle; D004578:Electron Spin Resonance Spectroscopy; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008567:Membranes, Artificial; D010713:Phosphatidylcholines / Q000378:metabolism*; D049294:Phospholipid Transfer Proteins; D011485:Protein Binding; D013113:Spin Labels
D000727:Androgen-Binding Protein; D002352:Carrier Proteins; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D049294:Phospholipid Transfer Proteins; D013113:Spin Labels