Inherited Sialoglycoprotein Deficiencies in Human Erythrocytes of Type En(a -)

Abstract

The membranes of erythrocytes were studied from a family in which there is a genetic defect (previously described as the En(a-) condition) resulting in the loss of the major erythrocyte sialoglycoprotein (PAS-I). Two different types of sialoglycoprotein deficiency can be distinguished within this family. The En(a-) group of variants is more appropriately described as a class of sialoglycoprotein deficient erythrocytes. The blood group M antigen of normal erythrocytes is found only on the erythrocyte sialoglycoprotein while in this family the M antigen is found on membrane components other than the sialoglycoprotein. The amino acid sequence of the sialoglycoprotein may be important in defining the difference between the blood group M and N antigens in normal erythrocytes.