Iodination of the Human Platelet Membrane

Abstract

Abstract Human platelet surfaces were labeled with radioactive iodide utilizing lactoperoxidase and hydrogen peroxide generated by a glucose oxidase-glucose system. Subcellular fractionation and electron microscopic autoradiography revealed that the radioactive label was primarily associated with the external plasma membrane. Sodium dodecyl sulfate acrylamide gel electrophoresis of the solubilized membrane proteins revealed intense labeling of a 100,000 molecular weight membrane glycoprotein which was not altered by thrombin. Several lesser peaks of isotopic labeling were also detected. Neuraminidase treatment of intact platelets significantly decreased the labeling of the major surface glycoprotein. Partial purification of the labeled surface glycoprotein was achieved by extraction from isolated cell membranes with lithium diiodosalicylate. Concanavalin A agglutinated the intact washed platelets and precipitated the isolated membrane glycoprotein. Affinity chromatography using bound concanavalin A was utilized to purify the membrane surface protein.