A novel bacterial metal-ion sensing and detoxification system

FERNANDO C. SONCINI; SUSANA K. CHECA; MARTÍN ESPARIZ; MARÍA E. PÉREZ AUDERO

Pinamar, Buenos Aires, Argentina.

Congreso; 10th congress of Panamerican Association for Biochemistry and Molecular Biology (PABMB), 41th Annual Meeting of Argentine Society for Biochemistry and Molecular Biology (SAIB), 20th Annual Meeting of Argentine Society for Neurochemistry (SAN).; 2005

Sociedad Argentina de Bioquímica y Biología Molecular.

  The MerR family is a group of transcriptional regulators with similar N-terminal DNA binding regions and C-terminal effector binding domains that respond specifically to certain environmental stimuli, such as heavy metals, oxidative stress or antibiotics. Among the heavy metal responsive regulators, different subfamilies can be distinguished based on key residues in their sequences, including a group that recognizes Cu(I); a separate group that specifically senses divalent metals such as Zn(II), Co(II), Cd(II), and Pb(II); and the group of Hg(II) responsive regulators. My group has characterized a three-gene Salmonella-specific locus coding for a protein with high homology to the MerR-like copper-responsive regulators, a metal-transporting P-type ATPase, and a polypeptide with homology to copper chaperones. Activation of this locus depends on both the intactness of the regulator and micromolar concentration of Au(III) salts in the culture medium, and it is not affected by addition of other mono or divalent heavy metal cations. In addition, a strain deleted in the locus was highly susceptible to gold salts, highlighting its role in gold detoxification. This is the first gold sensing and detoxification system identified in bacteria. This horizontally acquired system allows Salmonella to monitor and to withstand environments with high concentration of gold salts.