Type 1 and 3 M-proteins of Streptococcus pyogenes: peptic extraction and fibrinogen binding properties

Abstract

The pepsin extraction of group A type 1 streptococci for the isolation of M protein fragments was studied at different pH values and at different time intervals. The extracts were compared by SDS PAGE and fused rocket immunoelectrophoresis. Type 1 M protein fragments were prepared in preparative scale by pepsin extraction of type 1 streptococci at pH 5.5 for 60 min. The fragments were separated by affinity chromatography on immobilized fibrinogen and finally purified for sequence studies by gel chromatography. Pepsin extraction of group A type 3 streptococci was also studied at different pH values. In contrast to type 1, the SDS PAGE pattern changed drastically in dependence on the pH. Affinity chromatography on immobilized fibrinogen is also effective in the separation of the pH 5.5 type 3 streptococcal pepsin extract.