ISOLATION AND COMPLETE AMINO-ACID-SEQUENCE OF THE BETA-POLYPEPTIDE AND ALPHA-POLYPEPTIDE FROM THE PERIPHERAL LIGHT-HARVESTING PIGMENT-PROTEIN COMPLEX-II OF RHODOBACTER-SULFIDOPHILUS

The peripheral light-harvesting bacteriochlorophyll-carotenoid-protein complex B800-850 (LHII) has been isolated from membranes of semi-aero bic dark-grown cells of Rhodobacter sulfidophilus strain W4. A reverse d-phase HPLC system resolved one beta- and one alpha-polypeptide in th e ratio 1:1. The material obtained was of high purity and suitable for direct microsequence analysis. The primary structures of the beta- an d alpha-polypeptides have been determined. The beta-polypeptide consis ts of 51 amino acid residues, yielding a molecular mass of 5512 Da and having 64.7% hydrophobicity. The alpha-polypeptide consists of 52 ami no acid residues, with a calculated molecular mass of 5661 Da and 75% hydrophobicity. The significance of uncommon structure motives with re spect to the unusual spectroscopic characteristics of this light-harve sting complex is discussed.