Interaction of the yeast phosphatidylserine transfer protein with artificial and biological membranes.

Transfer of pyrene-labeled phosphatidylserine catalyzed by the yeast phosphatidylserine transfer protein in vitro largely depends on the membrane lipid composition of artificial unilamellar acceptor vesicles. Negatively charged phospholipids markedly decrease the rate of protein-catalyzed phosphatidylserine transfer. Although biological membranes contain a significant proportion of negatively charged phospholipids they serve more effectively as acceptors than artificial membranes with a similar phospholipid composition, but without proteins. This result indicates that proteins present in biological membranes mask negative charges of phospholipids on the surface of acceptor membrane vesicles. When proteins of the membrane surface are removed by proteinase treatment this protective effect is partially lost. A correlation between the activity of the phosphatidylserine transfer protein in yeast cytosol and the extent of membrane biogenesis during growth could not be observed.