Involved in the repression of the monooxygenase EthA which is responsible of the formation of the active metabolite of ethionamide (ETH). Inhibited by tert-butyl 4-(3-thiophen-2-yl-1,2,4-oxadiazol-5-yl) piperidine-1-carboxylate (RF1) and 1-(thiophen-2-ylacetyl)-4-(3-thiophen-2-yl-1,2,4-oxadiazol-5-yl)piperidine (RF3). Homodimer. Cells lacking this gene leads to ETH hypersentivity. Binding of inhibitors to EthR induces a conformational change in this repressor, which is then unable to bind its DNA operator, consequently allowing for increased transcription of EthA and bioactivation of ethionamide (ETH).