The arsRBC operon in E. coli contains three genes that are involved in the detoxification of arsenite, arsenate and antimonite in the cell. The operon can be repressed by the arsenical resistance operon repressor, encoded by one of the genes in the operon. It binds to the promoter region of the operon, preventing transcription. The first gene, arsR, encodes the arsenical resistance operon repressor, which inhibits the transcription of the operon. However, in the presence of arsenic, arsenate, antimony and bismuth, its repression of the operon is removed, and the genes can be properly transcribed. The second gene, arsB, encodes an arsenical pump membrane protein which likely forms the channel of an arsenite pump that confers arsenical resistance to the cell. The finalg gene in the operon, arsC, encodes arsenate reductase, an enzyme that reduces arsenate to arsenite, creating a molecule that the arsenical pump can move out of the cell.

Operon: Arsenical Resistance References