Structural analysis of the Ss sialoglycoprotein specific for Henshaw blood group from human erythrocyte membranes

Abstract

The N-terminal structures of the MN and Ss erythrocyte membrane sialoglycoproteins (glycophorins A. B) from 2 Henshaw (He) blood-group heterozygotes were determined by manual sequencing of tryptic glycopeptides and various secondary fragments. No structural alteration of the MN glycoprotein was detected. The He-specific portion of the Ss glycoprotein exhibited the N-terminal sequence Trp-Ser-Thr-Ser-Gly- (+ =glycosylation). Thus it differs at 3 positions from its normal counterpart which possesses N activity and exhibits the N-terminal structure Leu-Ser-Thr-Thr-Glu-. Analysis of the Ss glycoprotein from 15 He-negative erythrocyte samples did not reveal any of the 3 He-specific structural alterations. The presence of a glycine residue at the 5th position of the blood-group-M-active MN glycoprotein as well as in the He-specific Ss glycoprotein provides an explanation for the occurrence of antisera (anti-Me) reacting with the M and He antigens.