The inactivity of brain phospholipid transfer protein toward phosphatidylinositol 4-phosphate.

Bovine brain phosphatidylinositol transfer protein catalyzes the transport of phosphatidylinositol and, to a lesser extent, phosphatidylcholine between model phospholipid membranes. To investigate the transport of phosphorylated phosphatidylinositol derivatives, 32P-labeled lipids were isolated from guinea pig brain, separated by chromatography on a column of neomycin-coated glass beads, and incorporated into single bilayer vesicles. Under conditions where significant transfer of phosphatidylinositol was observed, no protein-catalyzed transport of phosphatidylinositol 4-phosphate was detected. Thus, the substrate specificity of the brain phospholipid transfer protein cannot be extended to phosphatidylinositol 4-phosphate.