N-Blood group

The terminal o- -NeuAC -[2->6]-0-fi-6al unit of the former exists as end-group in human serrotransferrin (13) and the a- -NeuAc -[2 3]-6-fi-Gal exists as end-group in the human M and N blood groups substances (14). 

Specificity of the M and N blood groups apparently lies in the protein moieties of the cell surface. Wasniowska et al. (1977) have indicated that the major structural difference between the antigens of the M and N blood groups is in the N-terminal amino acids, which are serine and leucine, respectively. In addition, the amino acid presumably at position 5 of each peptide is glycine for the M group and glutamic acid for the N group. 

Wasniowska, K., Drzeniek, Z., and Lisowska, E., 1977, The amino acids of M and N blood group glycopeptides are different, Biochem. Biophys. Res. Commun. 76 385. 

Lisowska, E., and Duk, M., 1975a, Modification of amino groups of human-erythrocyte glycoproteins and the new concept on the structural basis of M and N blood-group specificity, Ear. J. Biochem. 54 469. 

The results concerning the N-terminal structures of glycophorins A" and A were based on the labels that were placed on the crucial, N-terminal amino group, and they clearly showed that the amino acid residues at position S may play only a minor, if any, role in determining the structure of the MN blood-group determinants. The carbohydrate residues appear... 

As mentioned earlier, glycophorin B carries the N and the Ss blood-group antigens. It is known that the first 26 residues of the amino acid sequence are identical to those in the N-terminal portion of glycophorin A". Moreover, relative to glycophorin A, it has a shortened amino acid chain, comprising 35 amino acid residues at the C-terminus. It is also known to contain 4 lysine residues. 

The possible role that the lysine residues, N-terminal amino acid residues, and carbohydrate residues may play in the display of the MN blood-group determinants by glycophorins A, A, and has been investigated. Assuming that the N-terminal amino acid in each of these glycoproteins plays a prominent role in the display of the MN blood-group determinant, labels were placed on the N-terminal amino acid residues of the glycoproteins. 

It is now well established that the MN blood-group antigens are situated99-101 on the major sialoglycoprotein (glycophorin A) of the erythrocyte membrane. The complex, antigenic structure resides within the first five amino acid residues from the N-terminal portion of the molecule three of these residues are glycosylated. 

Nakajima, M., Ito, N., Nishi, K., Okamura, Y., and Hirota, T. (1988) Cytochemical localization of blood group substances in human salivary glands using lectin-gold complexes. /. Histochem. Cytochem. 36, 337-348. 

Gerhard, M., Lehn, N., Neumayer, N., Boren, T., Rad, R., Schepp, W., Miehlke, S., Classen, M., and Prinz, C. (1999). Clinical relevance of the Helicobacter pylori gene for blood-group antigen-binding adhesin. Proc. Natl. Acad. Sci. USA 96,1277 12783. 

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