Chlorosome proteins studied by MALDI-TOF-MS: topology of CsmA in Chlorobium tepidum.
Chlorosomes, the light-harvesting apparatus of green bacteria, are a unique antenna system, in which pigments are organized in aggregates rather than associated with proteins. Isolated chlorosomes from the green sulphur bacterium Chlorobium tepidum contain 10 surface-exposed proteins. Treatment of chlorosomes from Chlorobium tepidum with protease caused changes in the spectral properties of bacteriochlorophyll c and digestion of chlorosome proteins. Using SDS-PAGE analysis, immunoblotting and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) we have investigated the topology of the 59-residue CsmA protein. Our results show that at the N-terminus, the only amino acid available for protease degradation is the methionine. At the C-terminus, amino acids can be removed by protease treatment to produce a residual protein containing at least the sequence between residues 2 and 38. These results indicate that the N-terminal portion of the CsmA protein, which is predicted to be mainly hydrophobic, is buried in the chlorosome envelope.
Milks
Kirstin J
KJ
Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark.
Danielsen
Marianne
M
Persson
Søren
S
Jensen
Ole Nørregaard
ON
Cox
Raymond P
RP
Miller
Mette
M
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D041883:Chlorobium / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D015388:Organelles / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013057:Spectrum Analysis
D001426:Bacterial Proteins; C404706:CsmA protein, Chlorobium tepidum; D008565:Membrane Proteins