Binding of streptococcal lipoteichoic acid to the fatty acid binding sites on serum albumin

Abstract

The ability of the fatty acid binding sites of serum albumin to bind lipoteichoic acid of Streptococcus pyogenes was investigated. Initial studies indicated that lipoteichoic acid, but not its deacylated deprivative, protected albumin from being denatured by heat (80C for 1 h) and changed its mobility in an electrical field. Albumin covalently linked to agarose beads bound radiolabeled lipoteichoic acid, and the bound [3H]lipoteichoic acid could be specifically eluted with unlabeled lipoteichoic acid or albumin but not with other proteins tested. After binding to albumins, the lipoteichoic acid also could be quantitatively eluted with 50% ethanol and various detergents but not with up to 1.0 M sodium chloride. Binding of lipoteichoic acid to albumin followed first order kinetics, reaching saturation at 12 h. Analysis of the binding data by a Scatchard plot indicated heterogeneity of the binding sites on the albumin molecule similar to that previously reported for fatty acids. The affinity of binding of lipoteichoic acid to albumin was found to be intermediate between that previously reported for octanoic and palmitic acids, respectively. Based on these findings, we prepared affinity columns of immobilized albumin and were able to separate biologically active lipoteichoic acid from heterogeneous extracts of S. pyogenes.