title: Isolation and characterization of cytoplasmic membranes and chlorosomes from the green bacterium Chloroflexus aurantiacus.
abstract: A method was developed which allows the isolation and purification of cytoplasmic membranes and chlorosomes from cells of Chloroflexus aurantiacus grown under different light conditions. The dipolar ionic detergent Deriphat (0.08%) and a sodium iodide gradient centrifugation were used in isolating cytoplasmic membranes. Chlorosomes were prepared with 0.16% of the dipolar ionic detergent Miranol and purified by a sucrose gradient centrifugation. Cytoplasmic membrane fractions prepared from either high- (3,000 W m-2), medium-(200 W m-2) or low- (7 W m-2) light-grown cells had near infrared absorption bands at 866, 808, and 755 nm in a constant characteristic absorbance ratio of 6:3.8:1. In all cytoplasmic membrane preparations, the amount of bacteriochlorophyll a (Bchl a) per cytochrome, the amount of Bchl a per reaction center, and reaction center per milligram of cytoplasmic membrane protein was found to be constant. No Bchl c was present. Five respiratory enzyme activities have been measured in the cytoplasmic membrane fraction. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of denatured cytoplasmic membrane showed many bands, but a major polypeptide with an apparent molecular weight of 8,000. In contrast, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified chlorosomes did not contain the 8,000-molecular-weight band but revealed only three distinct protein bands with molecular weights of 15,000, 12,000, and 6,000. Isolated chlorosomes contained Bchl c and a small, yet constant, amount of Bchl a (absorbing at 790 nm) in a molar ratio of 25:1. The data indicated that the components of the photosynthetic apparatus in the cytoplasmic membrane of Chloroflexus aurantiacus remained constant and only the amount of antenna Bchl c varied with light conditions.
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis*; D001429:Bacteriochlorophylls / Q000032:analysis*; D002458:Cell Fractionation; D002462:Cell Membrane / Q000032:analysis; D002734:Chlorophyll / Q000031:analogs & derivatives*; D008027:Light; D009940:Organoids / Q000032:analysis; D010788:Photosynthesis; D012245:Rhodospirillales / Q000032:analysis / Q000254:growth & development / Q000648:ultrastructure*
chemical_list: D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; C026083:bacteriochlorophyll A proteins, Bacteria; D002734:Chlorophyll