title: Incorporation of light-harvesting complex I alpha and beta polypeptides into the intracytoplasmic membrane of Rhodobacter capsulatus.
abstract: The light-harvesting complex I (LHI) of Rhodobacter capsulatus is an oligomer of basic subunits each consisting of the two different pigment-binding polypeptides LHI alpha and LHI beta, encoded by the pufA (LHI alpha) and pufB (LHI beta) genes. Pulse-labeling experiments showed that in the presence of the LHI alpha polypeptide, the LHI beta polypeptide was inserted earlier into the intracytoplasmic membrane than was the LHI alpha polypeptide. Each of the pufA and pufB genes was deleted to test whether the LHI alpha and beta polypeptides, respectively, are inserted into the intracytoplasmic membrane independently of the LHI partner polypeptide. Neither deletion mutant strain formed the LHI antenna, but a functional reaction center complex was present. Pulse-labeling experiments indicated that the LHI beta polypeptide was inserted into the intracytoplasmic membrane with the same kinetics and in the same amounts regardless of whether the LHI alpha polypeptide was present. However, the LHI beta polypeptide did not accumulate in the membrane in the absence of the LHI alpha protein but was degraded linearly within about 12 min. In contrast to the LHI beta protein, only trace amounts of the LHI alpha polypeptide were inserted into or attached to the membrane if the LHI beta polypeptide was not synthesized.
authors.affiliation: Institut für Biologie II, Mikrobiologie, Albert-Ludwigs-Universität, Freiburg, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Richter
authors.forename: G
authors.initials: G
authors.lastname: Drews
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D001483:Base Sequence; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D002872:Chromosome Deletion; D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D045332:Photosystem II Protein Complex; D010860:Pigments, Biological / Q000378:metabolism; D010957:Plasmids; D016354:Rhodobacter capsulatus / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D008565:Membrane Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010860:Pigments, Biological; C023693:protein complex B800-850, Rhodobacter; C069404:protein complex B806-866, Chloroflexus aurantiacus