title: Membranes of Rhodospirillum rubrum: physicochemical properties of chromatophore fractions isolated from osmotically and mechanically disrupted cells.
abstract: Isolation of highly purified membrane fractions from phototrophically grown Rhodospirillum rubrum was achieved by velocity and isopyknic sedimentation under carefully controlled ionic conditions. Bacteriochlorophyll-rich and succinic dehydrogenase-rich chromatophores that were essentially devoid of contamination by non-chromatophore protein were separated from a denser fraction in extracts disrupted in a French pressure cell. Highly purified chromatophores and a nearly photopigment-free envelope fraction were also obtained from cells lysed by treatment with ethylenediaminetetraacetate-lysozyme-Brij 58. After lysis with lysozyme and ethylenediaminetetraacetate alone, about 50% of the total photosynthetic pigment was released in chromatophores similar to those isolated by the above procedures. Chromatophores prepared by each method were found to have very similar near-infrared absorption spectra, overall chemical composition, equilibrium buoyant densities in CsCl, and protein patterns in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The protein profiles of the dense, outer membrane-rich fractions were different from those of the chromatophores. The release of much of the photosynthetic apparatus as discrete chromatophores is osmotically lysed extracts necessitates a reevaluation of the concept that isolated chromatophores arise only from mechanical comminution of a larger membrane structure.
mesh_terms: D020130:Bacterial Chromatophores / Q000032:analysis; D001426:Bacterial Proteins / Q000032:analysis; D001429:Bacteriochlorophylls / Q000032:analysis; D002241:Carbohydrates / Q000032:analysis; D002458:Cell Fractionation; D003580:Cytochromes / Q000032:analysis; D004492:Edetic Acid / Q000494:pharmacology; D009113:Muramidase / Q000494:pharmacology; D009995:Osmosis; D010743:Phospholipids / Q000032:analysis; D012247:Rhodospirillum rubrum / Q000032:analysis* / Q000648:ultrastructure; D013501:Surface-Active Agents / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D002241:Carbohydrates; D003580:Cytochromes; D010743:Phospholipids; D013501:Surface-Active Agents; D004492:Edetic Acid; D009113:Muramidase