Role and molecular mechanism of the Rcs regulatory system in the Salmonella enterica serovar Typhimurium pathogenesis

DELGADO, MONICA ALEJANDRA

Sao Pablo

Conferencia; XXI Congreso Latinoamericano de Microbiología; 2012

Asociación Latinoamericana de Microbiología

The Rcs regulatory system consists of three proteins: the sensor RcsC, the response regulator RcsB; and the intermediary in the phosphoryl transfer RcsD. Those proteins are involved in complex multistep His-Asp-His-Asp phosphorlay pathways that act in the following order: RcsC-RcsD-RcsB, in which is possible that RcsC and RcsD interact to activate the RcsB regulator. We previously demonstrated that rcsB overexpression modulates the RcsB-dependent genes in an rcsC or rcsD mutant but not in the double mutant. These results suggest that only RcsB-P, the phosphorylated form, is able to induce this modulation, and we postulated that RcsB-P would occur by two or more different pathways. The Rcs system has an important role in the bacterial physiology, controlling capsule synthesis, motility and virulence behaviors, as well as in other cellular activities of Salmonella. The goal of this work was study the RcsB-phosphorelay pathways required to control the above physiological activities under different growth conditions. In this work we analyzed the interaction of the protein components in the Rcs network, at molecular levels. The in vivo bacterial two-hybrid assay (BACTH), allowed us to determine the potential interactions between the Rcs component proteins, specifically the interaction of RcsC with itself and with the intermediary RcsD. These interactions were also investigated by in vitro crosslinking assay, allowing us to determine the ability of the RcsC and RcsD purified cytosolic domains to form dimmer or oligomers. To validate the above observations, the phosphorelay pathway involved in the control of different RcsB-dependent physiological behavior was elucidated. These results represent the first evidence of RcsCDB-phosphorelay complexity pathways that the bacteria use for the gene regulation, highlighting the important role that this system plays in the different steps of the Salmonella pathogenesis.