title: Effect of heat and 2-mercaptoethanol on intracytoplasmic membrane polypeptides of Rhodopseudomonas sphaeroides.
abstract: Solubilization at 75 degrees C of Rhodopseudomonas sphaeroides chromatophores in the presence of sodium dodecyl sulfate (SDS) and 2-mercaptoethanol (beta-ME) resulted in the selective absence of reaction center B and C polypeptides from SDS-polyacrylamide gel electrophoresis profiles. A newly identified, chromatophore-specific polypeptide, with a mass of 35.2 kdaltons, was also missing under these conditions of chromatophore solubilization. Solubilization at 27 degrees C in the presence of SDS and beta-ME also resulted in the disappearance of these three polypeptides, but at much slower rates. Disappearance of either endogenous or exogenously supplied reaction center polypeptides B and C during SDS solubilization of whole chromatophores at either 27 or 75 degrees C was shown to be entirely dependent upon the presence of beta-ME. After chromatophore solubilization in the presence of beta-ME and subsequent SDS-polyacrylamide gel electrophoresis, exogenously added reaction centers B and C could be localized in a complex of no less than 100 to 200 kdaltons. However, the precise size of the complex was influenced by the stoichiometry of the reacting components. The disappearance of the 35.2-kdalton polypeptide was neither dependent upon the presence of beta-ME nor dependent upon the presence of any additional chromatophore polypeptides. The 35.2-kdalton polypeptide underwent a heat-induced oligomerization to yield several high-molecular-weight species.
mesh_terms: D020130:Bacterial Chromatophores / Q000032:analysis*; D001426:Bacterial Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D006358:Hot Temperature; D008623:Mercaptoethanol / Q000494:pharmacology*; D010455:Peptides; D011487:Protein Conformation / Q000187:drug effects; D012242:Rhodobacter sphaeroides / Q000032:analysis* / Q000648:ultrastructure; D012967:Sodium Dodecyl Sulfate
chemical_list: D001426:Bacterial Proteins; D010455:Peptides; D012967:Sodium Dodecyl Sulfate; D008623:Mercaptoethanol