Insights into the mechanism of signalling in the Rcs system

Trabajo presentado en el SEBBM19madrid - 42nd Congress of the Spanish Biochemical and Molecular Biology Society, celebrado en Madrid (España) del 16 al 19 de julio de 2019(Póster. G09-38-P43) The Rcs system present in enterobacteria plays a crucial role in motility, capsule and bio#12;lm formation upon sensing envelop integrity [1]. It is composed of an outer and an inner membrane proteins named RcsF and IgaA, respectively, involved in signal detection where IgaA is essential, and of the phosphorelay system RcsCDB that senses and transduces the signal to the cytoplasm [2]. The RcsCDB system comprises the hybrid histidine kinase RcsC, the phosphotransferase RcsD and the response regulator RcsB. While RcsC and RcsD are also bound in the inner membrane RcsB acts as a transcriptional factor to activate or inhibit expression of target genes. Upon stimuli detection by RcsF and IgaA, RcsCDB transduces the signal catalysing a phosphorelay cascade that starts with autophosphorylation of RcsC, followed by phosphotransfer to RcsD which in turn transfers the phosphoryl group to RcsB for its activation. RcsB is a master piece of the Rcs system controlling multiple genes either alone, inhibiting transcription of the hDC agellar master operon [3] or activating expression of the small regulatory RNA rprA, or interacting with auxiliary transcriptional factors such as RcsA to regulate the operon wca -also named cps involved in synthesis of colanic acid capsule [4] in a phosphorylationdependant or independent manner [5]. Our goal is to decipher the molecular bases involved in the sensing and transducing mechanism of the Rcs system. For that purpose, we are producing all components of the Rcs system to conduct functional and structural studies. In that sense, we have recently solved several structures of RcsB from S. typhimurium that has allowed us to visualize the conformation competent for DNA binding and provide understanding on the phosphorylation mechanism [6]. With that information we have generated several mutant variants of RcsB that have been [...