Identification of liver plasma membrane glycoproteins which bind to 125I-Labelled concanavalin A following electrophoresis in sodium dodecyl sulfate

Abstract

Following electrophoresis of ovalbumin in sodium dodecyl sulfate (SDS) this glycoprotein bound 125I-labeled Concanavalin A (Con A). The reaction was specific and proportional to the amount of glycoprotein present on the gel. This technique was used to study the Con-A-binding glycoproteins of liver cell surfaces. Mouse liver plasma membranes were purified and subfractionated to yield 2 fractions corresponding to the bile canalicular surface and the surface between adjacent hepatocytes. Both fractions bound 125I-labeled Con A, the former binding 2-3 times more lectin than the latter. Following SDS gel electrophoresis individual membrane glycoproteins reacted with 125I-labeled Con A. Both membrane subfractions yielded qualitatively similar Con A binding profiles, 7 binding proteins being present in each. The results are consistent with a generally uniform distribution of glycoproteins over the hepatocyte surface. The reaction of lectins with glycoproteins following SDS gel electrophoresis should find general application in the study of membrane composition.