A Sialoglycopeptide from Human Erythrocytes with Receptor-like Properties for Encephalomyocarditis and Influenza Viruses

Abstract

SUMMARYEncephalomyocarditis and influenza viruses attach to human erythrocytes causing haemagglutination. The receptor for both viruses on these cells is the major membrane sialoglycoprotein, glycophorin, solubilized preparations of which inhibit haemagglutination by either virus. We show here that glycophorin preparations inhibited haemagglutination of both viruses, even after the preparations were digested with chymotrypsin. To determine which component(s) in the digest exhibited activity, peptides separated by gel filtration were assayed for haemagglutination inhibition; one peptide only, CH-0, was active. A tentative structure was deduced for CH-0 from amino acid and sialic acid analyses. It was already known that neuraminidase treatment of erythrocytes or glycophorin prevents interaction with either virus, suggesting that sialic acid may form part of the active binding site in the receptor. However, receptor activity requires more than the presence of a particular arrangement of sialic acid since the arrangement in CH-0 was identical to that in two other inactive chymotryptic peptides. Examination by gel filtration, sucrose density gradient centrifugation and SDS-polyacrylamide gel electrophoresis demonstrated that CH-0 readily aggregated, unlike the inactive peptides. It was proposed that the CH-0 chymotryptic peptide showed receptor-like activity (inhibited haemagglutination) because its tendency to aggregate allowed strong multivalent binding with virus particles.

Analysis of the Bond between Encephalomyocarditis Virus and Its Human Erythrocyte Receptor by Affinity Chromatography on Virus-sepharose Columns

“…The present study indicates that the second hypothesis is probably correct. A requirement for multivalent binding would also explain why only that chymotryptic peptide of glycophorin, CH0 which includes the hydrophobic transmembrane region and which readily aggregates (Burness & Pardoe, 1983), binds to EMC virus.…”

“…Recovery was considerably improved by incorporating this detergent (Table 2), as described above for glycophorin. The relative binding of the chymotryptic peptides to EMC virus-Sepharose was parallel to the inhibition of haemagglutination by these peptides (Burness & Pardoe, 1983).…”

“…1311_labelled chymotryptic peptides of glycophorin, purified by gel filtration (Burness & Pardoe, 1983), were kindly supplied by I.U. Pardoe.…”

“…When individual peptides were applied to the column, it was found that peptides CH1, CH2 and CH3 showed little specific binding (Table 2) although all are sialylated (Burness & Pardoe, 1983). In contrast, a much larger proportion of peptide CH0 bound specifically to the column (Table 2).…”

“…In contrast, a much larger proportion of peptide CH0 bound specifically to the column (Table 2). Peptide CH0 is sialylated but in addition contains a transmembrane region (Burness & Pardoe, 1983). In the absence of sodium deoxycholate in the buffer, the recovery of peptide CH0 was poor, presumably due to aggregates being trapped at the top of the column.…”