PHOSPHOLIPID TRANSFER IN YEAST - ISOLATION AND PARTIAL CHARACTERIZATION OF A PHOSPHOLIPID TRANSFER PROTEIN FROM YEAST CYTOSOL

Yeast cytosol stimulates the intermembrane transfer of phospholipids. This was tested in vitro using radioactively labeled phospholipid vesicles as donor and mitochondria as acceptor membranes. A phospholipid transfer protein from yeast cytosol was purified to homogeneity. The successive steps of purification comprised ammonium sulfate precipitation, gel filtration of Sephadex G-75, DEAE-Sephacel and hydroxylapatite chromatography and chromatofocusing. The isolated phospholipid transfer protein has a MW of 35,000 and an isoelectric point of 4.6. This protein facilitates the transfer of phosphatidylcholine and phosphatidylinositol in vitro. It is temperature-sensitive and loses 50% of its activity after an incubation at 48.degree. C for 10 min. The specific activity of the phospholipid transfer in a 100,000 .times. g supernatant from yeast is independent of the growth state of the culture. Glucose repression in cells grown aerobically or anaerobiosis has no influence on the phospholipid transfer activity as compared to cells grown under derepressed aerobic conditions or to stationary cells. Phospholipid transfer activity in yeast is not strictly linked to active membrane biogenesis.