Selective determinants involved in the CueR-like regulators/target promoters interaction

PÉREZ AUDERO, M. E.; PODOROSKA, B.; SUSANA KARINA CHECA; SONCINI, F. C.

Rosario

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2006

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Transcriptional regulators of the MerR family respond specifically to a variety of environmental stimuli, such as heavy metals. Salmonella has two MerR homologs that respond to monovalent metal ions: CueR, which is involved in copper homeostasis, and GodS, that we demonstrated previously to be the main responsible for gold detoxification. Both regulators share similarities not only at protein level, but also in the sequence they recognize at the promoters of their target genes. Therefore, we analyzed whether these regulators can functionally replace each other. Using single and double mutant strains we demonstrated that in the absence of GodS, CueR induces small level expression of GodS-controlled genes, and vice versa. By electrophoretic mobility shift (EMSA) and DNAse I footprinting assays we found differences in the binding affinity to the promoters that could explain the low-level cross regulation observed. An in silico analysis of the GodS and CueR controlled promoters revealed the presence of distinctive bases that could account for the regulator?s discrimination. The characterization of a series of mutant promoters allowed us to identify the selective bases directly involved in selective recognition by the specific regulator. Our results can contribute to better understand the molecular bases of the interaction between MerR like regulators and their target promoters.