The preparation of inside-out vesicles from methanogenic bacteria with protein cell walls was improved with regard to the preservation of structure and localization of membrane-bound proteins. Complexes similar to the methanoreductosome in the methanogenic bacterium Gö 1 [1] were also found attached to the inner aspect of the cytoplasmic membrane of Methanococcus voltae. Methanoreductosomes were purified from crude extracts of Gö 1-cells by affinity chromatography. Under specific conditions at high protein concentrations methyl-CoM-methylreductase molecules isolated from Gö 1-cells could be reassociated to spherical complexes of various sizes, with an appearance similar to that of methanoreductosomes isolated from strain Gö 1.
