Electrophoretic and immunoelectrophoretic analysis of pig epidermal plasma membrane glycoproteins

he glycoprotein components of a plasma membrane-enriched fraction from pig epidermis were isolated by deoxycholate extraction and affinity chromatography on concanavalin A (ConA)-Sepharose 4B. Reduction with 5% 2-mercaptoethanol, electrophoresis on 10% polyacrylamide slab gels, and periodic acid-Schiff (PAS) staining resolved the major glycoproteins into at least 5 components of Mr 180K, 150K, 130K, 100K and 85K. Neuraminidase removed essentially all the sialic acid whether or not the glycoproteins were solubilized with detergents. Neuraminidase treatment increased the electrophoretic mobility of most components on one-dimension polyacrylamide gels, indicating their sialoglycoprotein nature. An antiserum was raised in rabbits against isolated epidermal plasma membrane glycoproteins. Isolated immunoglobulins were used in crossed immunoelectrophoretic analysis of the glycoproteins and produced 5 major immunoprecipitates. The glycoprotein nature of the immunoprecipitates was shown by their susceptibility to neuraminidase. Crossed immunoelectrophoresis was used to examine the lectin binding specificity of isolated epidermal plasma membrane glycoproteins. The immunoprecipitation patterns were affected strongly by Ricinus communis agglutinin (RCA), moderately by wheatgerm agglutinin (WGA), and weakly by soybean agglutinin (SBA). Peanut agglutinin (PNA), Dolichos biflorus agglutinin (DBA), and Ulex europaeus agglutinin (UEA) had little effect on the immunoprecipitation patterns, indicating little interaction between epidermal plasma membrane glycoprotein and these lectins. Other glycoproteins and/or glycolipids must therefore be responsible for the binding of these lectins by epidermal cells.