Abstract
The transmembrane organization of concanavalin A receptor proteins in purified plasma membranes from guinea pig peritoneal exudate macrophages was investigated. Inside-out vesicles prepared from the plasma membrane by affinity chro-matography on concanavalin A-Sepharose remained permeable to con-canavalin A and could be labelled from the outside only with immobilized lactoperoxidase-catalysed radio-iodination. After detergent solubliization, concanavalin A receptor proteins were isolated from the radio-iodinated inside-out vesicles and their mobilities were analyzed by electrophoresis in poly-acrylamide gels containing sodium dodecyl sulfate; this was followed by autoradiography. By these procedures, four iodinated proteins with apparent molecular weights of approximately 147, 000, 125, 000, 102, 000 and 77, 000 were specifically retained in the concanavalin A-Sepharose affinity columns, evidence that these glycoproteins span the plasma membrane.
