It is well known that SpeB, which is considered

a cysteine protease, degrades M protein on the cell surface and releases the fragments into the supernatant (22, 23). Unexpectedly, a considerable amount of M protein was detected in the culture supernatant proteins of all of the 29 strains tested, in spite of the presence of E-64, which specifically inhibits SpeB protease activity. Herwald et al. have reported a unique pathogenic potential of the emm1 and emm3 strains, a portion of whose M proteins are released into the supernatant where they form complexes with fibrinogen which induce vascular leakage (7). In this study, likewise, M protein was detected in the supernatants of emm6 and 12 strains, raising the possibility that these strains also possess this uncommon pathogenic mechanism. The observations obtained so far imply that csrS gene mutations cause production of large amounts of virulence-associated Inhibitor Library research buy proteins, including M protein, which is essential to the shift from a

pharyngeal to an invasive transcriptome profile (9, 19, 20). The mutations that have been reported to date are of the frameshift variety, causing truncated CsrS forms and a single amino acid substitution in the protein; such mutations are assumed sufficient find more to induce dysfunction or structural instability. In fact, the region proximal to the C-terminal has been reported to be crucial to phosphorylation (19). The fact that two of the M protein-high producers in this study carried two substitutions may underline the importance of the accumulation of point mutations, in addition to those at the mutation site, which

can eventually cause drastic change in the enzymatic activity or configuration of the CsrS protein. However, a significant difference between M protein-high and-low producers in emm gene transcription was not found in the TaqMan analysis. Mirabegron Of the 138 S. pyogenes strains from mild streptococcal infections, most of which were obtained from non-sterile sites, two strains expressed large amounts of M protein; interestingly, these two strains carried two amino acid substitutions in CsrS protein (2/138, 1.4%). Of the S. pyogenes strains clinically isolated from STSS cases, 34.8% carried a csrS mutation; significantly fewer mutations (1.69%) being found in non-STSS S. pyogenes strains (24). Taken together, our results and those of others clearly indicate that the frequency of csrS mutation is largely dependent on the colonization site, for example, whether S. pyogenes occurs on the pharynx or skin versus a subcutaneous site. Interestingly, four emm3 strains, including one of the M protein-high producers, did not have any csrS or csrR mutations. It appears, therefore, that M protein expression is controlled by several different regulatory genes including csrRS, mga and pel (10, 21, 25). Thus, the expression of emm3 may be regulated mainly by genes other than csrRS.