Serves as an oxidative stress sink, specifically for chlorite and hypochlorite. Part of the SigF regulon, induced by chlorite under positive control of SigF. Part of the probable yedZ1-yedY1-mrpX operon. Transcript levels are 20- to 60-fold increased when induced by chlorite or hypochlorite or in the absence of anti-sigma factor NrsF. Not induced by hydrogen peroxide. Protein is oxidized (possibly on Met residues) when cells are exposed to chlorite or hypochlorite; initially the protein is highly oxidized, by 50 minutes all protein is in the reduced form. Growth somewhat inhibited by chlorite.