title: Characterisation of the LH2 spectral variants produced by the photosynthetic purple sulphur bacterium Allochromatium vinosum.
abstract: This study systematically investigated the different types of LH2 produced by Allochromatium (Alc.) vinosum, a photosynthetic purple sulphur bacterium, in response to variations in growth conditions. Three different spectral forms of LH2 were isolated and purified, the B800-820, B800-840 and B800-850 LH2 types, all of which exhibit an unusual split 800 peak in their low temperature absorption spectra. However, it is likely that more forms are also present. Relatively more B800-820 and B800-840 are produced under low light conditions, while relatively more B800-850 is produced under high light conditions. Polypeptide compositions of the three different LH2 types were determined by a combination of HPLC and TOF/MS. The B800-820, B800-840 and B800-850 LH2 types all have a heterogeneous polypeptide composition, containing multiple types of both α and β polypeptides, and differ in their precise polypeptide composition. They all have a mixed carotenoid composition, containing carotenoids of the spirilloxanthin series. In all cases the most abundant carotenoid is rhodopin; however, there is a shift towards carotenoids with a higher conjugation number in LH2 complexes produced under low light conditions. CD spectroscopy, together with the polypeptide analysis, demonstrates that these Alc. vinosum LH2 complexes are more closely related to the LH2 complex from Phs. molischianum than they are to the LH2 complexes from Rps. acidophila.
authors.affiliation: Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, UK. Electronic address: anne-marie.carey@glasgow.ac.uk.
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Carey
authors.affiliation: Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, UK.
authors.forename: Kirsty
authors.initials: K
authors.lastname: Hacking
authors.affiliation: Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, UK.
authors.forename: Nichola
authors.initials: N
authors.lastname: Picken
authors.affiliation: Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, UK.
authors.forename: Suvi
authors.initials: S
authors.lastname: Honkanen
authors.affiliation: Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, UK.
authors.forename: Sharon
authors.initials: S
authors.lastname: Kelly
authors.affiliation: Photosynthetic Antenna Research Center, Washington University, St. Louis, MO 63130, USA.
authors.forename: Dariusz M
authors.initials: DM
authors.lastname: Niedzwiedzki
authors.affiliation: Photosynthetic Antenna Research Center, Washington University, St. Louis, MO 63130, USA; Department of Biology, Washington University, St. Louis, MO 63130, USA; Department of Chemistry, Washington University, St. Louis, MO 63130, USA.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Blankenship
authors.affiliation: Faculty of Science, Ibaraki University, 2-1-1 Bunkyo, Mito 310-8512, Japan.
authors.forename: Yuuki
authors.initials: Y
authors.lastname: Shimizu
authors.affiliation: Faculty of Science, Ibaraki University, 2-1-1 Bunkyo, Mito 310-8512, Japan.
authors.forename: Zheng-Yu
authors.initials: ZY
authors.lastname: Wang-Otomo
authors.affiliation: Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, UK.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Cogdell
keywords: Bacteriochlorophyll a; Carotenoid; Light-harvesting complex 2; Polypeptide; Purple sulphur bacteria; Spectroscopy