Binding of albumin fragments to surface receptor in A, C, and G streptococci.

Abstract

Fragments of human and bovine serum albumin were produced by treatment with trypsin at pH 8.15 and with pepsin at pH 3.5 and 3.7 in the presence of octanoic acid. A large fragment which included the C-terminal part of the native molecule was produced by trypsin treatment. The tryptic digest was subsequently treated with pepsin, resulting in smaller fragments. The ability of the fragments to bind to albumin-receptors on streptococci was investigated. According to Western blots only fragments with a mol. wt. of 23 kDa or more were able to bind to albumin-binding structures obtained from streptococci. The 23 kDa fragment was radiolabelled and tested for binding to whole bacteria. The fragment was capable of binding to albumin-reactive structures on group A, C, and G streptococci with the same species-specificity as native human and bovine serum albumin, respectively. Both the large 45 kDa tryptic fragment and the small 23 kDa fragment could bind to streptococci and could be dissociated by 2 M KSCN.