A 13C-methylation study of glycophorin A intact erythrocytes by 13C-NMR spectroscopy.
N-terminal N alpha-[13C]monomethylamino derivatives for the N-terminal serine and leucine residues of glycophorins AM and AN, respectively, were obtained by reductively 13C-methylating homozygous human erythrocytes (MM, NN). The 13C-labeled glycophorins, AM and AN, were then isolated. A unique structural state was observed in solution reductively 13C-methylated glycophorin AM that was not observed in glycophorin AM derived from 13C-methylated erythrocytes. We attribute this state to the fact that some of the glycophorin AM forms a head-to-head dimer when subjected to reductive 13 C-methylation in aqueous solution. The 13C chemical shift data and pH titration data for the N-terminal [13C]dimethylamino and [13C]monomethylamino groups of glycophorin AM and AN derived from reductively 13C-methylated erythrocytes were in agreement with the chemical shift and titration data previously obtained for the N-terminal [13C]dimethylamino groups of solution reductively 13C-methylated glycophorins and related glycopeptides and peptides and N-terminal [13C]monomethylamino groups of related glycopeptides and peptides.
D055598:Chemical Phenomena; D002621:Chemistry; D004912:Erythrocytes / Q000378:metabolism*; D006021:Glycophorins / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D008745:Methylation; D010084:Oxidation-Reduction; D011487:Protein Conformation; D012795:Sialoglycoproteins / Q000378:metabolism*
D006021:Glycophorins; D012795:Sialoglycoproteins