Glycophorin as a Receptor for Escherichia coli alpha-hemolysin in erythrocytes

Escherichia coli cu-hemolysin (HlyA) can lyse both red blood cells (RBC) an d liposomes, However, the cells are lysed at HlyA concentrations 1-2 orders of magnitude lower than liposomes (large unilamellar vesicles). Treatment of RBC with trypsin, but not with chymotrypsin, reduces the sensitivity of RBC toward HlyA to the level of the liposomes, Since glycophorin, one of th e main proteins in the RBC surface, can be hydrolyzed by trypsin much more readily than by chymotrypsin, the possibility was tested of a specific bind ing of HlyA to glycophorin, With this purpose, a number of experiments were performed. (a) HlyA was preincubated with purified glycophorin, after whic h it was found to be inactive against both RBC and liposomes, (b) Treatment of RBC with an anti-glycophorin antibody protected the cells against HlyA lysis, (c) Immobilized HlyA was able to bind glycophorin present in a deter gent lysate of RBC ghosts. (d) Incorporation of glycophorin into pure phosp hatidylcholine liposomes increased notoriously the sensitivity of the vesic les toward HlyA (e) Treatment of the glycophorin-containing liposomes with trypsin reverted the vesicles to their original low sensitivity, The above results are interpreted in terms of glycophorin acting as a receptor for Hl yA in RBC. The binding constant of HlyA for glycophorin was estimated, in R BC at sublytic HlyA concentrations, to be 1.5 x 10(-9) M.