Publications

• Characterization of unusual hydroxy- and ketocarotenoids in Rubrivivax gelatinosus: involvement of enzyme CrtF or CrtA.

  Pinta V., Ouchane S., Picaud M., Takaichi S., Astier C., Reiss-Husson F.

  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 characte ... >> More

  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. << Less

  Arch. Microbiol. 179:354-362(2003) [PubMed] [EuropePMC]

• Expression and biochemical characterization of the 1-HO-carotenoid methylase CrtF from Rhodobacter capsulatus.

  Badenhop F., Steiger S., Sandmann M., Sandmann G.

  In purple bacteria, acyclic 1-methoxy carotenoids like spheroidene or spirilloxanthin are essential components of the photosynthetic apparatus. One of the last steps of their biosynthesis involves O-methylation of the 1-hydroxy group. The 1-HO-carotenoid methylase CrtF from Rhodobacter capsulatus ... >> More

  In purple bacteria, acyclic 1-methoxy carotenoids like spheroidene or spirilloxanthin are essential components of the photosynthetic apparatus. One of the last steps of their biosynthesis involves O-methylation of the 1-hydroxy group. The 1-HO-carotenoid methylase CrtF from Rhodobacter capsulatus catalyzing this type of reaction was expressed in Escherichia coli in an active form. It was then purified by affinity chromatography and biochemically characterized. The enzymatic reaction depends on S-adenosylmethionine as the only cofactor. By complementation in E. coli, the substrate specificity of the enzyme was determined. It could be shown that the enzyme converts not only all possible 1-hydroxy carotenoids in the spheroidene/1'-HO-spheroidene biosynthetic pathway of R. capsulatus but also carotenoid intermediates leading to the formation of spirilloxanthin in a pathway which is absent in R. capsulatus but present in related species. << Less

  FEMS Microbiol. Lett. 222:237-242(2003) [PubMed] [EuropePMC]

• Biosynthesis of carotenoids derived from neurosporene in Rhodopseudomonas capsulata.

  Scolnik P.A., Walker M.A., Marrs B.L.

  We have characterized the carotenoids accumulated by a series of mutants of Rhodopseudomonas capsulata as part of a study of the synthesis, structure, and function of the photosynthetic membranes of this bacterium. The carotenoids in this study were identified by visible and mass spectroscopy, chr ... >> More

  We have characterized the carotenoids accumulated by a series of mutants of Rhodopseudomonas capsulata as part of a study of the synthesis, structure, and function of the photosynthetic membranes of this bacterium. The carotenoids in this study were identified by visible and mass spectroscopy, chromatography, derivatization, and chemical analyses. We have located a new genetic region, crtF, necessary for the O-methylation of the carotenoids. Mutants with a lesion in crtF accumulate demethylspheroidene as their major carotenoid during anaerobic growth and demethylspheroidenone when grown in the presence of oxygen, a heretofore undescribed phenotype. The genetic region necessary for O-methylation maps adjacent to the known cluster of genes affecting carotenoid biosynthesis. In addition, we have identified methoxyneurosporene as the carotenoid that preferentially binds to the reaction centers of strain Ga, a green mutant of R. sphaeroides which accumulates three neurosporene-like carotenoids. A metabolic grid for carotenoid biosynthesis is proposed, based upon the intermediates accumulated in these mutants. << Less

  J. Biol. Chem. 255:2427-2432(1980) [PubMed] [EuropePMC]