Structures of Miltenberger class I and II specific major human erythrocyte membrane sialoglycoproteins.

The N-terminal structure of the Miltenberger (Mi-) blood group class I and II specific human MN erythrocyte membrane sialogycoproteins were determined by manual sequencing of tryptic glycopeptides and various secondary fragments. The Mi-I and Mi-II active glycoproteins were found to exhibit a threonine → methionine and theonine → lysine exchange, respectively, at position 28 which prevents N-glycosylation of asparagines 26. Due to the absence of the N-glycosidic oligosaccharide chain the monomeric form of the Mi-I and Mi-II specific glycoproteins possesses a slightly increased sodium dodecyl sulfate/polyacrymide gel electrophoretic mobility, in comparison to its normal counterpart. Serological studies suggest that antibodies, specific for Mi-I or Mi-II red cells, react with the structurally altered region of the MN glycoprotein. [ABSTRACT FROM AUTHOR]