File:Model of pel regulation under the FleQ.jpeg

FleQ binds to two FleQ boxes on the pel promoter (A). FleQ interacts with FleN in the absence of ATP (B) as well as in the presence of ATP, but in this case, it induces a distortion of pel DNA (C). We propose that FleN forms a bridge between two FleQ bound to their binding sites. The binding of FleQ to FleQ box 2 is essential for repression. The binding of c-di-GMP to FleQ induces a conformational change of FleQ, probably propagated through FleN, which induces the relief of pel distortion and leads to pel expression (D). The binding of FleQ to FleQ box 1 is essential for activation.