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The pyelonephritogenic Escherichia coli strain 1 H 11165 specifically agglutinates human erythrocytes carrying the M blood group antigen. The polymorphic forms of this antigen, M and N, are located in the NH2-terminal region of the major human red-cell sialoglycoprotein, glycophorin A. Radioactively labeled glycophorin A from M cells specifically bound to the bacteria. Purified glycophorin AM, but not glycophorin AN, efficiently inhibited for binding. Mild periodate treatment oxidized the NH2-terminal serine in glycophorin AM and this resulted in loss of binding to the bacteria. High concentrations of serine and alkali-labile oligosaccharides derived from glycophorin AM inhibited the binding, whereas the synthetic M-specific NH2-terminal pentapeptide Ser-Ser-Thr-Thr-Gly did not. Neuraminidase treatment of glycophorin AM did not destroy the binding. The most efficient inhibition of binding was observed with the N-terminal glyco-octapeptide obtained from glycophorin AM by CNBr cleavage. This peptide contains both the essential serine residue and the alkali-labile oligosaccharides, which both are recognized by the bacterium.

The human erythroid cell line, K562, synthesizes the major red cell sialoglycoprotein, glycophorin A. We have isolated an mRNA fraction which codes for glycophorin A from K562 cells and studied the synthesis of the sialoglycoprotein in a rabbit reticulocyte cell-free system. In the absence of membranes a precursor form of glycophorin A was synthesized. This was identified using specific anti-(glycophorin A) serum. The apparent molecular weight of the carbohydrate-free precursor of glycophorin A was 19 500. This exceeds the molecular weight of the glycophorin A apoprotein by approximately 5000. In the presence of membranes from dog pancreas, the synthesized glycophorin A precursor was N-glycosylated and probably also O-glycosylated. The oligosaccharide chains remained incomplete and the glycoprotein synthesized in vitro corresponded to the glycosylated precursor of glycophorin A obtained in intact cells.