title: The photosynthetic membrane proteome of Rhodobacter sphaeroides R-26.1 exposed to cobalt.
abstract: Cells of the carotenoidless strain R-26.1 of Rhodobacter sphaeroides were grown in the presence of a high concentration (5 mM) of cobalt ions. The photosynthetic intracytoplasmic membranes were isolated and investigated by proteomic analysis using non-denaturating blue native electrophoresis in combination with LC-ESI-MS/MS. Comparison with intracytoplasmic membranes of cells grown under control conditions showed a change in the relative amount of proteins belonging to the photosynthetic apparatus, with net downregulation of light-harvesting complexes and increased concentration of the nude reaction center (RC), as well as upregulation of enzymes related to chemoorganotrophy. These effects represent possible bacterial adaptation so as to retrieve energy for metabolic processes from sources alternative to less efficient photosynthesis. The influence of cobalt on the photochemistry of the RC in cell extracts was also investigated by charge recombination. The kinetics of the charge recombination reaction was found to be slower in extracts from cells exposed to Co(2+), indicating that the reorganization of the photosynthetic apparatus also involves its photochemical core.
authors.affiliation: Italian National Research Council, Institute for Chemical-Physical Processes, Via Orabona 4, 70124 Bari, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Italiano
authors.forename: Gian Maria
authors.initials: GM
authors.lastname: D'Amici
authors.forename: Sara
authors.initials: S
authors.lastname: Rinalducci
authors.forename: Francesca
authors.initials: F
authors.lastname: De Leo
authors.forename: Lello
authors.initials: L
authors.lastname: Zolla
authors.forename: Raffaele
authors.initials: R
authors.lastname: Gallerani
authors.forename: Massimo
authors.initials: M
authors.lastname: Trotta
authors.forename: Luigi R
authors.initials: LR
authors.lastname: Ceci
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003035:Cobalt / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020543:Proteome / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012242:Rhodobacter sphaeroides / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D020543:Proteome; D003035:Cobalt