A PROTEOMIC ANALYSIS OF THE SALMONELLA RCSCDB SYSTEM UNRAVELING POST-TRANSCRIPTIONAL REGULATION OF METABOLIC GENES

ALBERTO PARADELA; JAVIER FERNANDO MARISCOTTI; ROSANA NAVAJAS; ANTONIO RAMOS-FERNANDEZ; JUAN PABLO ALBAR; FRANCISCO GARCÍA-DEL PORTILLO

Segovia

Congreso; 4th Congress of the Spanish Proteomics Society; 2011

Sociedad Española de Proteómica

The RcsCDB regulatory system of enteric bacteria has been shown to respond to signals as envelope stress and high osmolarity. The system is activated by a phosphorelay modulated by auxiliary proteins. An example is the Salmonella entérica membrane protein IgaA, which acts as an attenuator of the system. In our previous studies, we defined by transcriptomics more than 70 genes differentially expressed in bacteria carrying igaA mutations. In this work, we have extended these observations to a proteomic analysis based on ICPL-protein labeling followed by LC-ESI MS/MS analysis. A total of 505 unique proteins were identified and quantified, with 15% exhibiting statistically significant changes in response to distinct activation states of the RcsCDB system. Divergent expression at the RNA and protein level was also observed in a few cases. This feature was observed in the metabolic genes pckA, encoding the gluconeogenetic enzyme phosphoenolpyruvate carboxykinase, and metE, involved in the cobalamin-independent synthesis of methionine. In both cases, opposite transcriptional and translational patterns were observed. These findings were further confirmed by RTPCR and western-blot assays. Our proteomic and transcriptomic comparison therefore provided evidence for the existence of post-transcriptional regulatory phenomena implicating the RcsCDB system.