Membrane proteins of Rhodopseudomonas spheroides V. Additional chemical characterization of a pigment-lipid-associated protein isolated from chromatophores

The major protein component, Band 15, of the chromatophores of Rhodopseudomonas spheroides is associated with most of the pigments and phospholipids. The primary structure of Band 15 has been further characterized. Cyanogen bromide cleavage produced 3 oligopeptides which were present in equimolar amounts. The sum of the molecular weights of the oligopeptides derived from cyanogen bromide cleavage of Band 15 was 8600. This value compares favorably with the value of 11000 calculated from the methionine content of the protein. A C-terminal sequence, NH₂…Tyr-Ser-Glu-Glu-(Leu,Ala,Ala,Val,Val,Ala,Ala)-GlyCOOH, is proposed. A tryptic map of the protein has been obtained and the amino acid composition of each tryptic peptide determined.