Aerobic and anaerobic regulation of the <i>ubiCA</i> operon, encoding enzymes for the first two committed steps of ubiquinone biosynthesis in <i>Escherichia coli</i>

Abstract

The ubiCA operon of Escherichia coli encodes enzymes for the first two steps of ubiquinone biosynthesis. A monolysogen (ubiC-lacZ operon fusion) was constructed to study ubiCA regulation. Expression was higher during aerobic growth than anaerobically, and increased with rate of oxygen supply. Although ubiquinone is implicated in antioxidant roles, ubiC expression was not elevated in response to hydrogen peroxide or the redox cycling agent, paraquat. Glucose repressed expression and mutation of cya (encoding adenylate cyclase) increased expression. Anaerobically utilised electron acceptors (nitrite, nitrate, fumarate) did not affect expression. ubiC expression appears to be negatively regulated by Fnr and IHF.