Purification and characterization of the specific binding protein for platelet activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) from human platelets.

The binding protein to platelet activating factor (PAF) was solubilized with 2% Triton X-100 from human platelet membranes and purified approximately 23-fold by sequential chromatography on DEAE-cellulose, CM-cellulose and Sephadex G-200. The final preparation migrated as a single protein band corresponding to a radioactive peak of [3H]PAF bound on polyacrylamide disc gel electrophoresis. The molecular weight of the native form of the binding protein was estimated to be approximately 160,000 daltons by Sephadex G-200 column chromatography, and its isoelectric point was near 8.0. Exposure of the platelet membranes to an excess of unlabeled PAF diminished the binding of [3H]PAF.