Phospholipid transfer proteins catalyze the translocation of phospholipid molecules between natural and/or artificial membranes. A major class of these proteins exhibits specificity toward phosphatidylinositol and, to a lesser extent, phosphatidylcholine and is designated phosphatidylinositol transfer protein. A critical step in the catalytic mechanism is the formation of a complex between the transfer protein and a membrane surface, at which point protein-bound and membrane-bound phospholipid is exchanged. This research program is designed to further our understanding of phosphatidylinositol transfer proteins present in bovine and rat tissues. Efforts will be made to define the substrate binding domain of the transfer protein in terms of phospholipid-protein stoichiometry and fatty acyl chain specificity among a series of natural and synthetic phosphatidylinositols and phosphatidylcholines. Using polyclonal antibody raised against rat phosphatidylinositol transfer protein, the level and activity of transfer protein in gross anatomical regions of rat brain are quantitated and compared with the activities of important enzymes in the synthesis of phosphatidylinositol and phosphatidylcholine. Similar measurements are carried out with isolated neuronal, astroglial, and oligodendroglial cells. Changes in these activities as a function of central nervous system development are described. In addition, correlations between stimulated phosphoinositide metabolism and transfer protein levels and activity are made. Another specific goal is the isolation and characterization of the gene for rat phosphatidylinositol transfer protein. This phase of the research will yield not only a means of directing the synthesis of the protein in a suitable bacterial host and providing larger quantities of the protein for physical and chemical studies, but also information on the DNA and protein sequences which will lead to future investigations on the genetic regulation and catalytic mechanism of phosphatidylinositol transfer protein.
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