THE HEMAGGLUTININ OF STAPHYLOCOCCUS-SAPROPHYTICUS BINDS TO A PROTEIN-RECEPTOR ON SHEEP ERYTHROCYTES

Staphylococcus saprophyticus, an important cause of urinary tract infe ctions, produces two major surface proteins, the S. saprophyticus surf ace-associated protein (Ssp) and the hemagglutinin, which mediates fib ronectin binding and also functions as the major adhesin of the organi sm. The hemagglutinating and fibronectin binding functions probably re side on different parts of the molecule. To identify a receptor on euk aryotic cells, binding and inhibition studies with acidic and neutral glycosphingolipids, carbohydrates, and proteins of sheep erythrocyte m embranes were conducted. S. saprophyticus did not bind to any glycosph ingolipid and no inhibition was observed when hemagglutination assays were done in the presence of carbohydrates or fibronectin. Neither tre atment of erythrocytes with galactose oxidase or neuraminidase and gal actose oxidase nor mild periodate oxidation of erythrocytes reduced he magglutination. However, proteinase-treated erythrocytes were no longe r agglutinated. Similarly, untreated erythrocyte membranes inhibited h emagglutination, whereas proteinase-treated membranes did not. In addi tion, only hemagglutinating strains bound to 60- and 21-kDa sheep eryt hrocyte membrane proteins on ligand blots, and these proteins inhibite d hemagglutination. Our data indicate that, in contrast to many other hemagglutinins, the receptor on sheep erythrocytes for S. saprophyticu s is a protein.