The plasmin-binding protein Plr of group A streptococci is identified as glyceraldehyde-3-phosphate dehydrogenase

Group A streptococci bind the serine protease plasmin with high affinity. Previously, a 41 kDa protein was identified as a candidate plasmin receptor protein (Plr) from group A streptococcal strain 64/14. The plr gene encoding Plr was cloned and the deduced amino acid sequence of Plr had significant similarity to glyceraldehyde-3-phosphate dehydrogenases (GAPDHs). In this study we have isolated cytoplasmic GAPDH of streptococcal strain 64/14. This enzyme was examined, on both structural and functional levels, for its relatedness to the Plr of strain 64/14 purified from mutanolysin extract and to recombinant Plr. We report here that no differences were detected between streptococcal Plr and cytoplasmic GAPDH on the basis of antibody reactivity, plasmin-binding activity, GAPDH activity, N-terminal amino acid sequence, peptide map analysis by V8 protease digestion and amino acid composition analysis. Furthermore, the plr gene appears to be present as a single copy in group A streptococci.