Phosphorylation at the D53 but Not the T65 Residue of CovR Determines the Repression of <i>rgg</i> and <i>speB</i> Transcription in <i>emm</i> 1- and <i>emm</i> 49-Type Group A Streptococci

Abstract

CovR/CovS is a two-component regulatory system in group A Streptococcus (GAS). The D53 residue of CovR is phosphorylated by CovS, and the phosphorylated CovR D53 binds to the rgg-speB intergenic region and acts as the transcriptional repressor. Nonetheless, the transcription of rgg and Rgg-controlled speB is upregulated in the covR mutant but inhibited in the covS mutant. The present study showed that nonphosphorylated CovR D53 protein inhibits rgg and speB transcription in the presence of the phosphorylated CovR D53 in vivo , indicating that nonphosphorylated CovR D53 has a dominant role in suppressing rgg transcription. These results reveal the roles of nonphosphorylated CovR D53 in regulating rgg transcription, which could contribute significantly to invasive phenotypes of covS mutants.