A Salmonella specific transcriptional regulator that responds to gold

SUSANA KARINA CHECA; BOTTA, P.; SPINELLI, S. V.; SONCINI, F. C.

Bariloche

Congreso; Bariloche Protein Symposium, Argentine Society for Biochemistry and Molecular Biology XXXIX Annual Meeting; 2003

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

The MerR family is a group of transcriptional regulators with similar N-terminal helix-turn-helix DNA binding regions and C-terminal effectors binding regions that respond specifically to certain environmental stimuli, such as heavy metals, oxidative stress or antibiotics. We searched for new transcriptional regulators in Salmonella enterica serovar Typhimurium and identified a gene with high homology in sequence to members of the merR family of metalloregulatory proteins. This gene, hmrR, was located within a Salmonella specific region of the genome. hmrR forms a two-gene operon with a gene coding for a putative metal-transporting P-type ATPase (hmrT), and is located upstream to a gene showing high similarity to a family of metal binding proteins (hmrB). We showed here that HmrR regulates the expression of the two neighbouring genes, and probably its own synthesis. By measuring -galactosidase activity, we found that expression of these genes is strongly regulated by gold, but responds poorly to copper or silver ions, as well as other heavy metals. We mapped hmrT and hmrB promoters by primer extension analysis and noticed that their promoter/operator regions have signature elements that distinguish promoters controlled by transcriptional regulators of the MerR family: a suboptimal spacing between -10 and -35 elements and sequences of dyad symmetry. To our knowledge, this is the first example of a metalloregulatory protein that responds specifically to gold.