Fatty acid binding sites of serum albumin as membrane receptor analogs for streptococcal lipoteichoic acid

The ability of bovine serum albumin to inhibit the binding of group A streptococcal lipoteichoic acid (LTA) to human cells was investigated. Albumin blocked the ability of LTA to sensitize erythrocytes to agglutinate in the presence of anti-LTA in a dose-dependent manner. The inhibition of LTA binding to erythrocytes was demonstrated directly with radiolabeled LTA. At an albumin/LTA molar ratio of 1.5:1, albumin binding of the radiolabeled LTA to erythrocytes was inhibited by 45%. Analysis of the binding of radiolabeled LTA to erythrocytes in the presence of albumin indicated that albumin competitively inhibited the binding of LTA to putative cell membrane receptors, indicating that albumin and erythrocytes both bind to the same moiety on the LTA molecule.