title: ubiI, a new gene in Escherichia coli coenzyme Q biosynthesis, is involved in aerobic C5-hydroxylation.
abstract: 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.
authors.affiliation: Commissariat à l'Energie Atomique, Institut de Recherches en Technologies et Sciences pour le Vivant, Laboratoire Chimie et Biologie des Métaux, F-38054 Grenoble, France.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Hajj Chehade
authors.forename: Laurent
authors.initials: L
authors.lastname: Loiseau
authors.forename: Murielle
authors.initials: M
authors.lastname: Lombard
authors.forename: Ludovic
authors.initials: L
authors.lastname: Pecqueur
authors.forename: Alexandre
authors.initials: A
authors.lastname: Ismail
authors.forename: Myriam
authors.initials: M
authors.lastname: Smadja
authors.forename: Béatrice
authors.initials: B
authors.lastname: Golinelli-Pimpaneau
authors.forename: Caroline
authors.initials: C
authors.lastname: Mellot-Draznieks
authors.forename: Olivier
authors.initials: O
authors.lastname: Hamelin
authors.forename: Laurent
authors.initials: L
authors.lastname: Aussel
authors.forename: Sylvie
authors.initials: S
authors.lastname: Kieffer-Jaquinod
authors.forename: Natty
authors.initials: N
authors.lastname: Labessan
authors.forename: Frédéric
authors.initials: F
authors.lastname: Barras
authors.forename: Marc
authors.initials: M
authors.lastname: Fontecave
authors.forename: Fabien
authors.initials: F
authors.lastname: Pierrel
mesh_terms: D000332:Aerobiosis / Q000502:physiology; D001665:Binding Sites / Q000502:physiology; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005182:Flavin-Adenine Dinucleotide / Q000235:genetics / Q000378:metabolism*; D006867:Hydrolases / Q000235:genetics / Q000378:metabolism*; D006900:Hydroxylation / Q000502:physiology; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D014451:Ubiquinone / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D029968:Escherichia coli Proteins; C000619498:UbiI protein, E coli; D014451:Ubiquinone; D005182:Flavin-Adenine Dinucleotide; D006899:Mixed Function Oxygenases; D006867:Hydrolases
keywords: Coenzyme Q; Crystal Structure; Escherichia coli; Flavin; Hydroxylase; Monooxygenase; ubi Genes