Glycophorin A in two patients with congenital dyserythropoietic anemia type I and type II is partly unglycosylated.

Abstract

Glycophorins A from erythrocyte membranes of two patients with congenital dyserythropoietic anemia type I and type II (CDA type I and II) were analyzed for carbohydrate molar composition employing a modification of the recently published method that allowed simultaneous determination of carbohydrates and protein in electrophoretic bands of glycoproteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (Zdebska & Kościelak, 1999, Anal Biochem., 275, 171-179). The modification involved a preliminary extraction of erythrocyte membranes with aqueous phenol, subsequent electrophoresis and analysis of the extracted glycophorins rather than electrophoresis and analysis of the glycophorin from intact erythrocyte membranes. The results showed a large deficit of N-acetylgalactosamine, galactose, and sialic acid residues in glycophorin A from patients with CDA type I and type II amounting to about 45% and 55%, respectively. The results strongly suggest that glycophorin A in these patients is partly unglycosylated with respect to O-linked glycans. In addition, glycophorin A from erythrocytes of a patient with CDA II but not CDA I exhibited a significant deficit of mannose and N-acetylglucosamine suggesting that its N-glycosylation site was also partly unglycosylated.