Possible role of the carbohydrate residues in the display of the MN blood group determinants by glycophorin A.
Heterozygous glycophorin AM,N and homozygous glycophorin AM were reductively methylated with 13C-enriched formaldehyde in the presence of cyanoborohydride. Total reductive methylation modified the five lysine residues, and the N-terminal amino acid residues (serine and leucine) of glycophorins AM and AN, respectively. The 13C resonances of the incorporated labels were monitored as a function of the degree of glycosylation of the glycoprotein. While minimal, if any, structural changes were observed near the N-terminal amino acid upon removal of alpha-D-N-acetylneuraminic acid residues, gross structural changes were observed when most of the oligosaccharide chains were removed. We also found that progressive methylation of the lysine residues of glycophorin AM may influence either the chemical shift of one of the nonequivalent methyl groups of the N alpha, N-[13C]dimethyl serine residue, or one of the two states of glycophorin AM.
D000818:Animals; D002241:Carbohydrates / Q000032:analysis*; D006021:Glycophorins / Q000032:analysis*; D006801:Humans; D008951:MNSs Blood-Group System; D009682:Magnetic Resonance Spectroscopy; D011817:Rabbits; D012795:Sialoglycoproteins / Q000032:analysis*
D002241:Carbohydrates; D006021:Glycophorins; D008951:MNSs Blood-Group System; D012795:Sialoglycoproteins