Association of bacteriochlorophyll a with the CsmA protein in chlorosomes of the photosynthetic green filamentous bacterium Chloroflexus aurantiacus
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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.
Original language | English |
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Journal | BBA General Subjects |
Volume | 1413 |
Issue number | 3 |
Pages (from-to) | 172-180 |
Number of pages | 9 |
ISSN | 0304-4165 |
DOIs | |
Publication status | Published - 1999 |
Bibliographical note
Keywords: Amino Acids; Bacterial Proteins; Bacteriochlorophylls; Chlorates; Chlorobi; Electrophoresis, Polyacrylamide Gel; Hexanols; Octoxynol; Sodium Hydroxide; Subcellular Fractions; Trypsin
ID: 14095798