Separation and purification of phospholipid exchange proteins in rat small intestinal mucosa.

The cytosol fraction of rat small intestinal mucosa stimulated the transfer of [32P]phosphatidylcholine and [32P]phosphatidylinositol from donor liposomes to acceptor liposomes. The proteins which catalyzed the exchanges were separated into three fractions by gel filtration on a Sephadex G-75 column and chromatography on DEAE-cellulose and CM-cellulose. One of the fractions was purified 340-fold and stimulated phosphatidylcholine exchange but not phosphatidylinositol exchange. The other two fractions were active in the stimulation of phosphatidylcholine exchange as well as phosphatidylinositol exchange. These two fractions were purified 35-fold and 44-fold over the cytosol fraction with respect to the phosphatidylinositol exchange activity.