title: Association of bacteriochlorophyll a with the CsmA protein in chlorosomes of the photosynthetic green filamentous bacterium Chloroflexus aurantiacus.
abstract: The protein assumed to be associated with bacteriochlorophyll (BChl) a in chlorosomes from the photosynthetic green filamentous bacterium Chloroflexus aurantiacus was investigated by alkaline treatment, proteolytic digestion and a new treatment using 1-hexanol, sodium cholate and Triton X-100. Upon alkaline treatment, only the 5.7 kDa CsmA protein was removed from the chlorosomes among six proteins detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis, concomitantly with the disappearance of BChl a absorption at 795 nm. Trypsin treatment removed two proteins with molecular masses of 11 and 18 kDa (CsmN and CmsM), whereas the spectral properties of BChl a and BChl c were not changed. By the new hexanol-detergent (HD) treatment, most BChl c and all of the detected proteins except CsmA were removed from the chlorosomes without changing the BChl a spectral properties. Subsequent proteinase K treatment of these HD-treated chlorosomes caused digestion of CsmA and a simultaneous decrease of the BChl a absorption band. Based on these results, we suggest that CsmA is associated with BChl a in the chlorosomes. This suggestion was supported by the measured stoichiometric ratio of BChl a to CsmA in isolated chlorosomes, which was estimated to be between 1.2 and 2.7 by amino acid analysis of the SDS-PAGE-resolved protein bands.
authors.affiliation: Department of Biology, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji, Tokyo, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Sakuragi
authors.forename: N
authors.initials: N
authors.lastname: Frigaard
authors.forename: K
authors.initials: K
authors.lastname: Shimada
authors.forename: K
authors.initials: K
authors.lastname: Matsuura
mesh_terms: D000596:Amino Acids / Q000032:analysis; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001429:Bacteriochlorophylls / Q000737:chemistry / Q000378:metabolism*; D002704:Chlorates; D019414:Chlorobi / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D000441:Hexanols; D017830:Octoxynol; D012972:Sodium Hydroxide; D013347:Subcellular Fractions / Q000737:chemistry; D014357:Trypsin
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D002704:Chlorates; D000441:Hexanols; D012972:Sodium Hydroxide; D017830:Octoxynol; D014357:Trypsin; C032706:sodium chlorate