The response regulator PhoP was found to play a key role in the repression of tlpA in conjunction with two other regulators , TlpA itself .
The response regulator PhoP was found to play a key role in the repression of tlpA in conjunction with two other regulators , RpoS itself .
Consistent with that , a putative PhoP binding motif was identified in the upstream region of tlpA , suggesting that PhoP may directly repress tlpA expression .
The presence of a PhoP binding sequence in the promoter region would indicate that the repression of tlpA by PhoP is direct ; however , further studies are needed in order to confirm this .