Arsenic biosorption mediated by arsenic-binding proteins QueF and QueE in sp. OR-15.

Microorganisms play a crucial role in arsenic transformation, with associated genes highly conserved within the operon. Although microorganisms can absorb arsenic, no specific genes responsible for intracellular sequestration have been found within this operon. This suggests that genes outside the operon may also contribute to bacterial arsenic resistance. Here, we identified an arsenic-resistant sp. OR-15 that exhibits consistent biosorption capacity for arsenic. Our findings indicate that the expression of heavy metal-related genes and , which are not located in the operon, is also induced by arsenite [As(III)]. When or is expressed in the arsenic-sensitive bacterium AW3110, it enhances both the resistance to As(III) and the biosorption capacity. Purified QueF and QueE demonstrate binding abilities for both As(III) and arsenate [As(V)]. Site-directed mutagenesis studies reveal that the conserved cysteine residue at position 101 in QueF and position 37 in QueE are critical for As(III) and As(V) binding. The transcriptional regulation mechanism involves the arsenic-responsive protein ArsR, which binds to the promoter region of the operon and regulates its expression. This study elucidates the molecular mechanisms underlying QueF/QueE-mediated arsenic biosorption in sp. OR-15.IMPORTANCEArsenic is a ubiquitous metalloid pollutant in the environment, and its bioavailable concentration significantly influences its toxicity. Microorganisms play a crucial role in the geochemical cycling of arsenic, with certain species capable of reducing its bioavailability through biosorption. Consequently, elucidating the mechanisms of bacterial biosorption of As(III) is essential. This study identifies arsenic-binding proteins, QueF and QueE, which are regulated by ArsR in sp. OR-15. These proteins can directly bind intracellular As(III), facilitating its biological fixation and mitigating the toxic effects of As(III) to cells. This discovery provides valuable insights into the microbial mechanisms of microbial arsenic biosorption.