Regulates transcription of a subregulon within the general stress response (PubMed:18643936). Exerts positive and negative effects in response to ethanol stress (PubMed:18643936). Activity is controlled at multiple levels (PubMed:22812682). Regulation includes a positive autoregulatory loop on mgsR transcription and a post-translational redox-sensitive activation step by an intramolecular disulfide bond formation in response to ethanol stress (PubMed:22812682). In addition, protein stability is strictly controlled by rapid proteolytic degradation by the ClpXP and ClpCP proteases (PubMed:22812682, PubMed:32477307). The McsB protein-arginine kinase might serve as a proteolytic adapter for the ClpX ATPase in the degradation mechanism of MgsR (PubMed:32477307). Expression is sigma B-dependent (PubMed:11544224, PubMed:18643936). Induced by ethanol, heat and salt stress (PubMed:11544224, PubMed:18643936). Positively autoregulated (PubMed:22812682). Deletion of the gene results in differential expression of approximately 70 genes in response to ethanol stress compared with the wild-type strain. Belongs to the ArsC family.