Resistance to toxic heavy metals in bacteria is controlled by cytoplasmic metalloregulators of the MerR family. These transcriptional activators bind metals ions with high affinity at the dimer interface, using residues from both monomers. According to th

MENDOZA JI; SONCINI FC; CHECA SK

Mendoza

Congreso; Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular.; 2018

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular.

Contamination with heavy toxic metals is a worldwide concern, affecting not only human health but also biodiversity. The use of whole-cell bacterial biosensors (WCB) emerges as a simple and cost-effective alternative to conventional detection procedures. Although poorly sensitive, these engineered bacteria report only the bioavailable fraction, being more appropriate to evaluate risk. Our group focuses on the study of metalloregulators, the key component of WCB and the main determinant of sensitivity. Previously, based on non-selective variants of GolS -the Salmonella Au(I) sensor/transcriptional regulator- we developed WCB for the simultaneous and high sensitivity detection of a broad-spectrum of metals including mercury (Hg), lead (Pb) and cadmium (Cd), which are among the most hazardous contaminants in the environment. Taking advantage of the unusual plasticity exhibited by GolS and its functional paralogue CueR, we applied site-directed mutagenesis on the metal binding region of these sensors to privilege recognition of Hg(II), Pb(II) or Cd(II). The functionality of the mutant sensors was evaluated by the activation of specific reporter genes in response to different metal ions. We obtained a set of GolS- or CueR-derived mutant sensors with altered metal recognition. GolS variants improved selectivity toward Hg(II) while analogous CueR-derivatives privileged recognition Pb and Cd in detriment of other metals, highlighting differences on the metalloregulator scaffolds. Our results indicate that is possible to improve selectivity of GolS or CueR to allow the development of specific WCB for reporting bioavailable Hg, Pb or Cd on the environment.