Photosynthesis Research

, Volume 86, Issue 1, pp 101–111

Isolation and Characterization of Carotenosomes from a Bacteriochlorophyll c-less Mutant ofChlorobium tepidum

  • Niels-Ulrik Frigaard
  • Hui Li
  • Peter Martinsson
  • Somes Kumar Das
  • Harry A. Frank
  • Thijs J. Aartsma
  • Donald A. Bryant
Regular Paper

DOI: 10.1007/s11120-005-1331-8

Cite this article as:
Frigaard, N., Li, H., Martinsson, P. et al. Photosynth Res (2005) 86: 101. doi:10.1007/s11120-005-1331-8

Abstract

Chlorosomes are the light-harvesting organelles in photosynthetic green bacteria and typically contain large amounts of bacteriochlorophyll (BChl) c in addition to smaller amounts of BChl a, carotenoids, and several protein species. We have isolated vestigial chlorosomes, denoted carotenosomes, from a BChl c-less, bchK mutant of the green sulfur bacterium Chlorobium tepidum. The physical shape of the carotenosomes (86 ± 17 nm × 66 ± 13 nm × 4.3 ± 0.8 nm on average) was reminiscent of a flattened chlorosome. The carotenosomes contained carotenoids, BChl a, and the proteins CsmA and CsmD in ratios to each other comparable to their ratios in wild-type chlorosomes, but all other chlorosome proteins normally found in wild-type chlorosomes were found only in trace amounts or were not detected. Similar to wild-type chlorosomes, the CsmA protein in the carotenosomes formed oligomers at least up to homo-octamers as shown by chemical cross-linking and immunoblotting. The absorption spectrum of BChl a in the carotenosomes was also indistinguishable from that in wild-type chlorosomes. Energy transfer from the bulk carotenoids to BChl a in carotenosomes was poor. The results indicate that the carotenosomes have an intact baseplate made of remarkably stable oligomeric CsmA–BChl a complexes but are flattened in structure due to the absence of BChl c. Carotenosomes thus provide a valuable material for studying the biogenesis, structure, and function of the photosynthetic antennae in green bacteria.

Copyright information

© Springer 2005

Authors and Affiliations

  • Niels-Ulrik Frigaard
    • 1
  • Hui Li
    • 1
  • Peter Martinsson
    • 2
    • 5
  • Somes Kumar Das
    • 3
  • Harry A. Frank
    • 3
  • Thijs J. Aartsma
    • 2
  • Donald A. Bryant
    • 1
  1. 1.Department of Biochemistry and Molecular BiologyThe Pennsylvania State UniversityUniversity ParkUSA
  2. 2.Department of BiophysicsLeiden UniversityLeidenThe Netherlands
  3. 3.Department of ChemistryUniversity of ConnecticutStorrsUSA
  4. 4.Department of Civil and Environmental EngineeringMassachusetts Institute of TechnologyCambridgeUSA
  5. 5.Institute of Medical TechnologyUniversity of TampereFinland