title: Structure of spheroidene in the photosynthetic reaction center from Y Rhodobacter sphaeroides.
abstract: The structure of the reaction center of Y Rhodobacter sphaeroides has been solved at 3 A resolution, using the atomic coordinates of the reaction center from the carotenoidless mutant R26 Rhodobacter sphaeroides. The structure has been refined by a stimulated annealing with the computer program X-PLOR, leading to a crystallographic R factor of 0.22 using reflections between 8 and 3 A. The spheroidene molecule which is bound to the Y reaction center has been fitted in the electron density map as a 15-cis isomer with a highly asymmetric structure. The cis-bond is located at proximity from ring 1 of the accessory bacteriochlorophyll on the inactive M side. The nature of the cis-bond was confirmed by resonance Raman spectra obtained from Y reaction center crystals. The structure of spheroidene in Y reaction center is compared to that proposed for 1,2-dihydroneurosporene in Rhodopseudomonas viridis reaction center crystals.
authors.affiliation: Institut de Chimie des Substances Naturelles, UPR 407, CNRS, Gif sur Yvette, France.
authors.forename: B
authors.initials: B
authors.lastname: Arnoux
authors.forename: A
authors.initials: A
authors.lastname: Ducruix
authors.forename: F
authors.initials: F
authors.lastname: Reiss-Husson
authors.forename: M
authors.initials: M
authors.lastname: Lutz
authors.forename: J
authors.initials: J
authors.lastname: Norris
authors.forename: M
authors.initials: M
authors.lastname: Schiffer
authors.forename: C H
authors.initials: CH
authors.lastname: Chang
mesh_terms: D001426:Bacterial Proteins / Q000302:isolation & purification*; D002338:Carotenoids / Q000302:isolation & purification*; D045342:Light-Harvesting Protein Complexes; D008958:Models, Molecular; D008968:Molecular Conformation; D045322:Photosynthetic Reaction Center Complex Proteins; D012242:Rhodobacter sphaeroides / Q000032:analysis*; D013059:Spectrum Analysis, Raman; D014961:X-Ray Diffraction
chemical_list: D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; C005637:spheroidene; D002338:Carotenoids