Interaction of the RcsB Response Regulator with Auxiliary Transcription Regulators in Eschericha coli [Microbiology]

December 3rd, 2015 by Pannen, D., Fabisch, M., Gausling, L., Schnetz, K.

The Rcs phosphorelay is a two-component signal transduction system that is induced by cell envelope stress. RcsB, the response regulator of this signaling system, is a pleiotropic transcription regulator, which is involved in the control of various stress responses, cell division, motility and biofilm formation. RcsB regulates transcription either as a homodimer or together with auxiliary regulators, such as RcsA, BglJ and GadE in Escherichia coli. In this study, we show that RcsB in addition forms heterodimers with MatA (=EcpR) and with DctR. Our data suggest that the MatA dependent transcription regulation is mediated by the MatA-RcsB heterodimer, and is independent of RcsB phosphorylation. Furthermore, we analyzed the relevance of amino acid residues of the active quintet that is coordinating phosphorylation, of conserved residues, as well as of surface exposed residues for activity of RcsB homo- and heterodimers. The data suggest that the activity of the phosphorylation-dependent dimers, such as RcsA-RcsB and RcsB-RcsB, is affected by mutation of residues in the vicinity of the phosphorylation site, suggesting that a phosphorylation-induced structural change modulates their activity. In contrast, the phosphorylation-independent heterodimers BglJ-RcsB and MatA-RcsB are affected by only very few mutations. Heterodimerization of RcsB with various auxiliary regulators and their differential dependence on phosphorylation thus adds an additional level of control to the Rcs system that is operating at the output level.