Abstract
The NH2-terminal sialoglycopeptides from human erythrocyte glycophorin A have been obtained by specific proteolytic cleavage and gel filtration chromatography. By cyanogen bromide cleavage, a glycosylated octapeptide was obtained from blood group M donors having an amino acid composition and 13C NMR spectrum consistent with the structure (formula: see text) was demonstrated. By Staphylococcus aureus protease cleavage, a glycosylated pentapeptide was obtained from N donors having the same structure as II, without the carboxyl-terminal sequence Val . Ala . Hse. Methanolysis/gas chromatographic analysis and 13C NMR spectroscopy of I and II and their asialo derivatives reveal that the M- and N-active sialoglyco-octapeptides both have identical oligosaccharide structures, each containing three O-linked tetrasaccharides with the structure NeuNAc alpha 2-3Gal beta 1-3(NeuNAc alpha 2-6)GalNAc alpha 1-O-Ser(Thr). The demonstration of the anomeric form of GalNAc-peptide linkages revealed by 13C NMR has previously been inaccessible by chemical analysis. Conformationally, I and II appear identical and both manifest several unusual resonance shifts suggestive of a glycopeptide secondary structure involving four specific hydrogen bonds. Calcium ion titration was also found to induce shifts in the NeuNAc 13C resonances that may be of functional significance. Serological studies reveal that both the M and N glyco-octapeptides and the N glyco-pentapeptide retain all of the M and N activity of the parent structure. Deamination and/or desialylation completely destroys this activity. These data are consistent with a model in which the M or N determinant is the NH2-terminal amino acid and a NeuNAc residue(s). From these data it is concluded that there is no chemical basis for assertions in the literature that M and N antigens differ in their oligosaccharide structure or that the N antigen is biosynthetically transformed to the M antigen by sialylation.
Highlights
The NH2-terminal sialoglycopeptides from human their oligosaccharide structure or that thNe antigen is erythrocyte glycophorin A have been obtained by spe- biosynthetically transformed to the M antigen by siacific proteolytic cleavage and gel filtration chromatog- lylation
By Staphylococcus aureus protease amino acid sequence and there is little informationavailable cleavage, a glycosylated pentapeptide was obtained on the individual oligosaccharide structures at each attachfrom N donors having the same structure as 11,without ment site
Having established the structure of the core saccharide of the asialoglycopeptides, the Gal and GalNAc carbons of the intact sialoglycopeptides I and I1 can be assigned if the tion (30), GalNAc-1 in the pl-0-Thr linkage is expected at NeuNAc linkage sites are known
Summary
Be isolated with a yield of 1.5 mg/100 mg of starting material, whichwas betterthan 80% pure(Table 11). Isolation and Chemical Analysis of NH2-terminal Octapeptides apparently was obtained by cleavage at the glutamic acid residue in position 5 of only the N-specific tryptic peptide. This cleavage is consistent with the specificity of the enzyme.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
