Purification of a light-harvesting B880 complex from wild-type Rhodospirillum rubrum

The light-harvesting B880 complex of Rhodospirillum rubrum was purified by a new method which allowed recovery of 66% of the amount present in the crude solubilized extract. Electrophoretic analysis of the isolated complex, followed by either Coomassie brilliant blue or silver staining, revealed only two low-molecular-weight polypeptides. When compared to a previously described preparation, the stability of the complex was considerably increased. In addition, the new procedure yielded B880 of higher purity as evidenced both by the decreased protein to pigment ratio (A280/A880 = 0.4) and by the absence of contaminants previously detected by silver staining or by an immunochemical method in other preparations. The most prominent of those contaminants were identified in this work as lipopolysaccharides of the bacterial outer membrane.