title: Characterization of the quinones in purple sulfur bacterium Thermochromatium tepidum.
abstract: Quinone distributions in the thermophilic purple sulfur bacterium Thermochromatium tepidum have been investigated at different levels of the photosynthetic apparatus. Here we show that, on average, the intracytoplasmic membrane contains 18 ubiquinones (UQ) and 4 menaquinones (MQ) per reaction center (RC). About one-third of the quinones are retained in the light-harvesting-reaction center core complex (LH1-RC) with a similar ratio of UQ to MQ. The numbers of quinones essentially remains unchanged during crystallization of the LH1-RC. There are 1-2 UQ and 1 MQ associated with the RC-only complex in the purified solution sample. Our results suggest that a large proportion of the quinones are confined to the core complex and at least five UQs remain invisible in the current LH1-RC crystal structure.
authors.affiliation: Faculty of Science, Ibaraki University, Mito 310-8512, Japan.
authors.forename: Yuuka
authors.initials: Y
authors.lastname: Kimura
authors.affiliation: Faculty of Science, Ibaraki University, Mito 310-8512, Japan.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Kawakami
authors.affiliation: Faculty of Science, Ibaraki University, Mito 310-8512, Japan.
authors.forename: Long-Jiang
authors.initials: LJ
authors.lastname: Yu
authors.affiliation: Faculty of Science, Ibaraki University, Mito 310-8512, Japan.
authors.forename: Miku
authors.initials: M
authors.lastname: Yoshimura
authors.affiliation: Institute of National Colleges of Technology, Ariake College, Omuta, Fukuoka 836-8585, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kobayashi
authors.affiliation: Faculty of Science, Ibaraki University, Mito 310-8512, Japan. Electronic address: wang@ml.ibaraki.ac.jp.
authors.forename: Zheng-Yu
authors.initials: ZY
authors.lastname: Wang-Otomo
mesh_terms: D002841:Chromatiaceae / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D003460:Crystallization; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry; D011809:Quinones / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013056:Spectrophotometry, Ultraviolet; D014451:Ubiquinone / Q000737:chemistry; D024482:Vitamin K 2 / Q000737:chemistry
chemical_list: D045342:Light-Harvesting Protein Complexes; D011809:Quinones; D024482:Vitamin K 2; D014451:Ubiquinone
keywords: Chromatophore; Electron transport; Light-harvesting; Photosynthesis; Reaction center