The polypeptide components from light-harvesting pigment-protein complex II (B800-850) of Rhodopseudomonas capsulata. Solubilization, purification and sequence studies.

A new procedure for isolation, purification and identification of the three polypeptides of the membrane-bound light-harvesting complex II (B800-850) of Rhodopseudomonas capsulata has been developed. The polypeptides were extracted from crude intracytoplasmic membranes with chloroform/methanol/ammonium acetate and separated by chromatography on Sephadex LH60. The peak fractions were transferred to solvents of different polarity and separated by gel filtration or ion-exchange chromatography. The three major polypeptides isolated by this two-step chromatography were found to be homogenous and identical with the three polypeptides of the light-harvesting complex II, as judged by amino acid analysis and N-terminal sequence determination. Contaminating minor polypeptides, of which the functions are unknown, were different from the polypeptides of the B800-850 complex studied by the same criteria.