Thermophilic arsenic binding proteins: characterization and exploitation as biosensors.

Arsenic is an ubiquitous toxic metalloid naturally present in the soil, water and air that adversely affects human health. The abundance of arsenic in the environment has guided the evolution of multiple defence strategies in almost all microorganisms which must therefore sense the metalloid and regulate the transcription of genes coding for resistance proteins. In this sense microorganisms participate to the geochemical cycling of arsenic in their living environments, promoting or inhibiting arsenic release from sediment material (1). The thermophilic gram negative bacterium Thermus thermophilus HB27 is able to grow in the presence of both arsenate and arsenite in a range of concentrations which are lethal for other microorganisms. The putative resistance genes have not been found in a single resistance operon but associated to chromosomal genes apparently not functionally related. One of them codes for a thioredoxin-coupled arsenate reductase (TtArsC) which catalyzes the reduction of pentavalent arsenate to trivalent arsenite (2); the second codes for a transcriptional repressor (TtSmtB), sensitive to arsenic, belonging to the ArsR/SmtB family of transcriptional regulators. Here we present studies addressed to the elucidation of the role of TtarsC and TtsmtB in the arsenic resistance mechanism, among which the characterization of the recombinant TtArsC and TtSmtB proteins. The results obtained represent the starting point for the development of stable whole-cell or protein- based arsenic biosensors (3). THIS WORK IS SUPPORTED BY GRANTS FROM THE REGIONE CAMPANIA, LEGGE 5 (ITALY, CUP NUMBER E69D15000210002), AND FROM THE PROJECT BIO2013-4496R. REFERENCES: 1 ROSEN BP . “BIOCHEMISTRY OF ARSENIC DETOXIFICATION”. FEBS LETTERS 2002; 529:86-92. 2. DEL GIUDICE I, ET AL. “A NOVEL ARSENATE REDUCTASE FROM THE BACTERIUM THERMUS THERMOPHILUS HB27: ITS ROLE IN ARSENIC DETOXIFICATION”. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:2071-2079. 3. POLITI J ET AL. “INTERACTION OF THERMUS THERMOPHILUS ARSC ENZYME AND GOLD NANOPARTICLES NAKED-EYE ASSAYS SPECIATION BETWEEN AS(III) AND AS(V). NANOTECHNOLOGY. 2015;26(43):435703