Proteins exposed on the outer surface of the plasma membranes of AH-66 hepatoma ascites cells.

The cell surface proteins of AH-66 hepatoma ascites cells were examined both by fluorescent labeling with cycloheptaamylose-fluorescamine complex and by radioiodination with lactoperoxidase. The labeled proteins were analyzed by measuring the distribution of fluorescence or radioactivity in polyacrylamide gels after electrophoresis. Although the degree of fluorescent labeling with cycloheptaamylose-fluorescamine complex was substantially different from that obtained by lactoperoxidase-catalyzed iodination, proteins with molecular weights of 130,000, 90,000, 86,000, 50,000--60,000, and 37,000 were strongly labeled in common by both reagents. It is suggested that at least these proteins are exposed on the surface of the plasma membranes of AH-66 cells. One of these proteins labeled strongly by both reagents is the major glycoprotein, with an apparent molecular weight of 130,000 in 10% polyacrylamide gels.