title: Localization of the exposed N-terminal region of the B800-850 alpha and beta light-harvesting polypeptides on the cytoplasmic surface of Rhodopseudomonas capsulata chromatophores.
abstract: Proteinase K and trypsin were used to determine the orientation of the light-harvesting B800-850 alpha and beta polypeptides within the chromatophores (inside-out membrane vesicles) of the mutant strain Y5 of Rhodopseudomonas capsulata. With proteinase K 7 amino acid residues of the B800-850 alpha polypeptide were cleaved off up to position Trp-7--Thr-8 of the N terminus, and 11 residues were cleaved off up to position Leu-11-Ser-12 of the beta chain N terminus. The C termini of the B800-850 alpha and beta polypeptides, including the hydrophobic transmembrane portions, remained intact. It is proposed that the N termini of the alpha and beta subunits, each containing one transmembrane alpha-helical span, are exposed on the cytoplasmic membrane surface and the C termini are exposed to or directed toward the periplasm.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D020130:Bacterial Chromatophores / Q000032:analysis* / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000032:analysis*; D002268:Carboxypeptidases; D019286:Endopeptidase K; D010450:Endopeptidases; D007425:Intracellular Membranes / Q000032:analysis; D045322:Photosynthetic Reaction Center Complex Proteins; D012241:Rhodopseudomonas / Q000032:analysis* / Q000648:ultrastructure; D014357:Trypsin
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D002268:Carboxypeptidases; D010450:Endopeptidases; C022633:serine carboxypeptidase; D014357:Trypsin; D019286:Endopeptidase K