ROLE OF THE RcsC/YojN/RcsB REGULATORY SYSTEM IN LPS MODIFICATION IN SALMONELLA TYPHIMURIUM

ESTELA CERASUOLO; ROBERTO MORERO; MÓNICA A. DELGADO

Rosario- Santa Fe (Argentina)

Congreso; XLII Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology (SAIB); 2006

SAIB

   Prokaryotic organisms respond to changing environmental conditions regulating the genes expression via two-component systems. The RcsC/YojN/RcsB phosphorelay system consists of the sensor protein RcsC, the cognate response regulator RcsB and the histidin-containing phosphotransfer protein YojN that is apparently used as an intermediary in the phosphoryl transfer from RcsC to RcsB.    We studied the role of Rcs system in the control of those genes involved in the Salmonella enterica virulence and determined that RcsC/YojN/RcsB and PmrA/PmrB regulatory systems promote wzzB (O-antigen chain length determinant gene) transcription under different environmental conditions and independently of each other. The transcriptional induction of the wzzB gene increased the amount of O-antigen in the LPS leading to a higher resistance to the serum complement-mediated killing. In addition, we identified a new role of the WzzB protein in the lipid A modification, indicating that the WzzB is required for many biological processes. We also demonstrated that the absence of pbgE2 and pbgE3 genes, which are regulated by the PmrA/PmrB system and involved in the lipid A modification, resulted in an O-antigen without the region containing 1 to 15 O-antigen subunits. These results indicated that both O-antigen formation and the lipid A modification are required at the same time during the Salmonella infection.