AUTHORS
J E Rebollar-Flores, L Medina-Aparicio, V E Osio-Becerro, J M Villarreal, S Mayo, B D Mendoza, S Rodríguez-Gutierrez, L Olvera, S Davila, S Encarnacion, G Martínez-Batallar, E Calva, I Hernández-Lucas
ABSTRACT
LtrR is a LysR-type regulator involved in the positive expression of ompR to promote ompC and ompF expression. This regulatory network is fundamental in the control of bacterial transformation and in resistance to the bile salt sodium deoxycholate in Salmonella enterica serovar Typhi. In this work, the transcriptional regulation of ltrR was characterized, revealing that the use of alternative promoters results in two transcripts. The larger one, ltrR2 mRNA was repressed at promoter and coding regions by H-NS, whereas Lrp repressed its expression at the coding region. In the case of the second and shorter ltrR1 transcript, it was only repressed at the coding region by H-NS and Lrp. Remarkably, pH 7.5 is a positive signal involved in the transcriptional expression of both ltrR units. Translational fusions and western blot experiments demonstrated that ltrR2 and ltrR1 mRNAs encode LtrR2 and LtrR1 proteins. This study adds new data on the complex genetic and regulatory characteristics of one of the most predominant transcriptional factors in bacteria, the LysR-type transcriptional regulators.
Importance: The LysR-type transcriptional regulators are present in virus, archaea, bacteria and in eukaryotic cells. Furthermore, these proteins are the most abundant transcriptional factors in bacteria. Here we demonstrate that two LysR-type proteins are generated from the ltrR gene. These proteins are genetically induced by pH and repressed at the promoter and coding regions by the global regulators H-NS and Lrp. Thus, novel basic aspects about the complex genetic regulation of the LysR-type transcriptional regulators are described.
Click here to read the article, published in the American Society for Microbiology.
