title: Characterization of unusual hydroxy- and ketocarotenoids in Rubrivivax gelatinosus: involvement of enzyme CrtF or CrtA.
abstract: Carotenoids are widely spread terpenoids found in photosynthetic organisms and a number of non-photosynthetic fungi and bacteria. The photosynthetic non-sulfur purple bacterium Rubrivivax gelatinosus produces carotenoids by both the spheroidene and the normal spirilloxanthin pathways. The characteristics of two carotenogenesis enzymes, spheroidene monooxygenase CrtA and O-methyltransferase CrtF, were investigated. Disruption of the corresponding genes by insertional mutagenesis affected carotenoid species in both pathways, and the genetic evidence indicated that both genes are involved in the two pathways. In these mutants, several unusual hydroxy- and ketocarotenoids were identified by spectroscopic and chemical methods. Moreover, the carotenoid analyses demonstrated that a large number of different carotenoid intermediates are accepted as substrates by the CrtA enzyme. The combined manipulation of crtF and crtA allowed new carotenoids to be produced and broadened the diversity of structurally different carotenoids synthesized by Rvi. gelatinosus. Methylated carotenoids, such as spheroidene and spirilloxanthin, are known to function as accessory pigments in the light-harvesting and reaction-center complexes of purple bacteria; the demethylated carotenoids described here were able to fulfill the same functions in the mutants.
authors.affiliation: Laboratoire de Génétique des Bactéries Photosynthétiques. Centre de Génétique Moléculaire, UPR2167 associée à l'Université Pierre-et-Marie-Curie, bât. 24 C.N.R.S., 91198, Gif-sur-Yvette cedex, France.
authors.forename: Violaine
authors.initials: V
authors.lastname: Pinta
authors.forename: Soufian
authors.initials: S
authors.lastname: Ouchane
authors.forename: Martine
authors.initials: M
authors.lastname: Picaud
authors.forename: Shinichi
authors.initials: S
authors.lastname: Takaichi
authors.forename: Chantal
authors.initials: C
authors.lastname: Astier
authors.forename: Françoise
authors.initials: F
authors.lastname: Reiss-Husson
mesh_terms: D001426:Bacterial Proteins / Q000502:physiology; D020562:Betaproteobacteria / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D002338:Carotenoids / Q000737:chemistry* / Q000145:classification / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003001:Cloning, Molecular; D005798:Genes, Bacterial; D008780:Methyltransferases / Q000235:genetics / Q000502:physiology*; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000502:physiology*; D008954:Models, Biological; D008957:Models, Genetic; D016254:Mutagenesis, Insertional
chemical_list: D001426:Bacterial Proteins; D002338:Carotenoids; D006899:Mixed Function Oxygenases; D008780:Methyltransferases