Publications

• ubiI, a new gene in Escherichia coli coenzyme Q biosynthesis, is involved in aerobic C5-hydroxylation.

  Hajj Chehade M., Loiseau L., Lombard M., Pecqueur L., Ismail A., Smadja M., Golinelli-Pimpaneau B., Mellot-Draznieks C., Hamelin O., Aussel L., Kieffer-Jaquinod S., Labessan N., Barras F., Fontecave M., Pierrel F.

  Coenzyme Q (ubiquinone or Q) is a redox-active lipid found in organisms ranging from bacteria to mammals in which it plays a crucial role in energy-generating processes. Q biosynthesis is a complex pathway that involves multiple proteins. In this work, we show that the uncharacterized conserved vi ... >> More

  Coenzyme Q (ubiquinone or Q) is a redox-active lipid found in organisms ranging from bacteria to mammals in which it plays a crucial role in energy-generating processes. Q biosynthesis is a complex pathway that involves multiple proteins. In this work, we show that the uncharacterized conserved visC gene is involved in Q biosynthesis in Escherichia coli, and we have renamed it ubiI. Based on genetic and biochemical experiments, we establish that the UbiI protein functions in the C5-hydroxylation reaction. A strain deficient in ubiI has a low level of Q and accumulates a compound derived from the Q biosynthetic pathway, which we purified and characterized. We also demonstrate that UbiI is only implicated in aerobic Q biosynthesis and that an alternative enzyme catalyzes the C5-hydroxylation reaction in the absence of oxygen. We have solved the crystal structure of a truncated form of UbiI. This structure shares many features with the canonical FAD-dependent para-hydroxybenzoate hydroxylase and represents the first structural characterization of a monooxygenase involved in Q biosynthesis. Site-directed mutagenesis confirms that residues of the flavin binding pocket of UbiI are important for activity. With our identification of UbiI, the three monooxygenases necessary for aerobic Q biosynthesis in E. coli are known. << Less

  J. Biol. Chem. 288:20085-20092(2013) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.

• Evolution of Ubiquinone Biosynthesis: Multiple Proteobacterial Enzymes with Various Regioselectivities To Catalyze Three Contiguous Aromatic Hydroxylation Reactions.

  Pelosi L., Ducluzeau A.L., Loiseau L., Barras F., Schneider D., Junier I., Pierrel F.

  The ubiquitous ATP synthase uses an electrochemical gradient to synthesize cellular energy in the form of ATP. The production of this electrochemical gradient relies on liposoluble proton carriers like ubiquinone (UQ), which is used in the respiratory chains of eukaryotes and proteobacteria. The b ... >> More

  The ubiquitous ATP synthase uses an electrochemical gradient to synthesize cellular energy in the form of ATP. The production of this electrochemical gradient relies on liposoluble proton carriers like ubiquinone (UQ), which is used in the respiratory chains of eukaryotes and proteobacteria. The biosynthesis of UQ requires three hydroxylation reactions on contiguous positions of an aromatic ring. In <i>Escherichia coli</i>, each of three UQ flavin monooxygenases (FMOs), called UbiF, UbiH, and UbiI, modifies a single position of the aromatic ring. This pattern of three hydroxylation reactions/three proteins has been accepted as a paradigm in UQ biology. Using a phylogenetic analysis, we found that UbiF, UbiH, and UbiI are detected only in a small fraction of proteobacteria, and we identified two new types of UQ FMOs: UbiM, which is distributed in members of the alpha, beta, and gamma classes of proteobacteria, and UbiL, which is restricted to members of the alphaproteobacteria. Remarkably, the <i>ubiL</i> and <i>ubiM</i> genes were found in genomes with fewer than three UQ hydroxylase-encoding genes. We demonstrated, using biochemical approaches, that UbiL from <i>Rhodospirillum rubrum</i> and UbiM from <i>Neisseria meningitidis</i> hydroxylate, respectively, two and three positions of the aromatic ring during UQ biosynthesis. We conclude that bacteria have evolved a large repertoire of hydroxylase combinations for UQ biosynthesis, including pathways with either three specialist enzymes or pathways with one or two generalist enzymes of broader regioselectivity. The emergence of the latter is potentially related to genome reduction events. <b>IMPORTANCE</b> UQ, a key molecule for cellular bioenergetics that is conserved from proteobacteria to humans, appeared in an ancestral proteobacterium more than 2 billion years ago. UQ biosynthesis has been studied only in a few model organisms, and thus, the diversity of UQ biosynthesis pathways is largely unknown. In the work reported here, we conducted a phylogenomic analysis of hydroxylases involved in UQ biosynthesis. Our results support the existence of at least two UQ hydroxylases in the proteobacterial ancestor, and yet, we show that their number varies from one to four in extant proteobacterial species. Our biochemical experiments demonstrated that bacteria containing only one or two UQ hydroxylases have developed generalist enzymes that are able to catalyze several steps of UQ biosynthesis. Our study documents a rare case where evolution favored the broadening of an enzyme's regioselectivity, which resulted in gene loss in several proteobacterial species with small genomes. << Less

  mSystems 1:e00091-16(2016) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.