Absence of the major sialoglycoprotein in the membrane of human En(a--) erythrocytes and increased glycosylation of band 3.

The human En(a-) blood group is a rare recessive trait. These erythrocytes lack the major membrane sialoglycoprotein (PAS1, MN protein, or glycophorin) and contain a decreased amount of PAS2 as demonstrated by radiolabeling of surface porteins and chemical techniques. A third glycoprotein, Band 3, contains two labeled oligosaccharide chains; the more complex oligosaccharide has a higher molecular weight in En(1-) cells than in normal cells. A fourth glycoprotein, PAS3, is present in usual amounts in En(a-) cells. Cells heterozygous for En(a) are intermediate in these respects. The sialic acid is decreased in En(a-) cells, but the total carbohydrate is similar in the different membranes. The glycolipids are present in normal amounts but are much more exposed to galactose oxidase in En(a-) cells than in normal cells.