Structural properties of the combining site of anti Streptococcus group a antibodies: Spin label-hapten studies

Abstract

The size of the combining site of anti Streptococcus group A antibodies has been examined by a set of spin label-haptens. The results indicate that the examined combining site has a structure large enough to envelop two glucopyranose rings. Furthermore it appears that the combining site cannot accomodate the branching residues of the polysaccharide antigen. The interaction between the lanthanide (III) ion and the hapten combining sites of anti streptococcal antibodies has been examined by e.s.r.-spectroscopy. It was demonstrated that the antagonistic interaction between the two sites previously observed in the myeloma protein MOPC 315 (Dwek et al., Biochem. J. 155, 37-53 (1976)), was also characteristic of the anti Streptococcus antibodies. The findings suggest that the antagonism between the two binding sites is a general features of antibodies. © 1977 Carlsberg Laboratory.