Despite the known hazardous effects of antimony (Sb) on human health, Sb monitoring biosensors have not been as actively investigated as arsenic (As) biosensors. Whole-cell bioreporters (WCBs) employing an arsenic-responsive operon and a regulatory protein (ArsR) are reportedly capable of monitoring arsenite, arsenate, and antimonite. However, the potential of WCBs as Sb biosensors has been largely ignored. Here, the metal-binding site of ArsR (sequenced as ELCVCDLCTA from amino acid number 30 to 39) was modified via genetic engineering to enhance Sb specificity. By relocating cysteine residues and introducing point mutations, nine ArsR mutants were generated and tested for metal(loid) ion specificity. The Sb specificity of WCBs was enhanced by the C37S/A39C and L36C/C37S mutations on the As binding site of ArsR. Additionally, WCBs with other ArsR mutants exhibited new target sensing capabilities toward Cd and Pb. Although further research is required to enhance the specificity and sensitivity of WCBs and to broaden their practical applications, our proposed strategy based on genetic engineering of regulatory proteins provides a valuable basis to generate WCBs to monitor novel targets.
Keywords: Antimony; ArsR; Arsenic-responsive operon; Protein engineering; Whole-cell bioreporters.