Ubiquinone (coenzyme Q) biosynthesis in Escherichia coli: identification of the ubiF gene

Ubiquinone (coenzyme Q; abbreviation, Q) plays an essential role in electro n transport in Escherichia coil when oxygen or nitrate is the electron acce ptor. The biosynthesis of Q involves at least nine reactions. Three of thes e reactions involve hydroxylations resulting in the introduction of hydroxy l groups at positions C-6, C-4, and C-5 of the benzene nucleus of Q. The ge nes encoding the enzymes responsible for these hydroxylations, ubiB, ubiH, and ubiF are located at 87? 66, and 15 min of the E. coil linkage map. The ubiF encoded oxygenase introduces the hydroxyl group at carbon five of 2-oc taprenyl-3-methyl-6-methoxy-1,4-benzoquinol resulting in the formation of 2 -octaprenyl-3-methyl-5-hydroxy-6-methoxy-1,4-benzoquinol. An ubiF mutant fa iled to early out this conversion. Based on the homology to UbiH, an open r eading frame (orf391) was identified at the 15 min region of the chromosome . amplified using PCR, and cloned into pUC18 plasmid. The ubiF mutants, whe n complemented with this plasmid, regained the ability to grow on succinate and synthesize (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.