Ubiquinone deficiency in an auxotroph of Escherichia coli requiring 4-hydroxybenzoic acid

Abstract

Escherichia coli 156:53D2 synthesized ubiquinone only when the growth medium was supplemented with 4-hydroxybenzoate acid. Little or no vitamin K2 was formed by the mutant under the growth conditions employed, in contrast with wild-type strains. In the mutant ubiquinone deficiency was correlated with low respiration and with low particulate NADH-oxidase and NADH-cytochrome b1-reductase activity. Preincubation of ubiquinone-deficient particles with ubiquinone-30 largely restored the NADH-oxidase and NADH-cytochrome b1-reductase activities. Various NADH-dye-linked reductases which may be associated with NADH dehydrogenase were not affected by the absence of ubiquinone. The succinate-oxidase complex was less affected than the particulate NADH oxidase by ubiquinone deficiency. A pathway for electrons in the NADH-oxidase complex of the auxotroph of E. coli is proposed and its relationship to the pathway in the wild-type strain is discussed.