GLYCOPROTEINS WITH GAL-ALPHA-4GAL ARE ABSENT FROM HUMAN ERYTHROCYTE-MEMBRANES, INDICATING THAT GLYCOLIPIDS ARE THE SOLE CARRIERS OF BLOOD-GROUP-P ACTIVITIES

The antigenic determinants of the blood group P family (P-1, P, P-k and LKE antigens) are chemically based on Gal alpha 4Gal. For human erythrocytes it has been claimed that the majority of P-1 determinants are expressed in glycoproteins, mainly band 4.5 (Haselberger, C. G., and Schenkel-Brunner, H. (1982) PEBS Lett. 149, 126-128). In the present work, the existence of Gal alpha 4Gal in glycoproteins of erythrocyte membranes (ghosts) of P-1 positive and negative human individuals was carefully analyzed on replicas of sodium dodecyl sulfate-polyacrylamide electrophoresis gels using specific reagents (Escherichia coli HB101/pDC1 expressing the Pop gene and monoclonal antibodies with specificities for P-1 and P-k antigens). No binding to glycoproteins was detected with any of these ligands when the ghosts had been pretreated with butanol to remove glycolipids. Therefore, all antigenic determinants of the P blood group family on human red cells are exclusively expressed in glycolipids and are absent from glycoproteins.