A new type of ArsR transcriptional repressor controls transcription of the arsenic resistance operon of Arsenicibacter rosenii SM-1.

Arsenic is the most common toxic metalloid in the environment. Nearly all organisms have genes for arsenic detoxification. Arsenic detoxification genes are frequently organized in chromosomal or plasmid-encoded arsenic resistance (ars) operons, which are commonly regulated by members of the ArsR transcriptional repressors. To date, three As(III)-responsive ArsRs with different As(III) binding sites have been identified. Here, we identify a new type of As(III)-responsive ArsR repressor that has an atypical As(III) binding site and controls transcription of the ars operon of Arsenicibacter rosenii SM-1. Our results provide new insights into the classification and evolution relationship of the ArsR transcriptional repressors.