TY - JOUR
T1 - Isolation and characterization of carotenosomes from a bacteriochlorophyll c-less mutant of Chlorobium tepidum
AU - Frigaard, Niels Ulrik
AU - Li, Hui
AU - Martinsson, Peter
AU - Das, Somes Kumar
AU - Frank, Harry A.
AU - Aartsma, Thijs J.
AU - Bryant, Donald A.
N1 - Funding Information:
This work was supported by Grant DE-FG02-94ER20137 to D.A.B. from the US Department of Energy. Research in the laboratory of H.A.F. is supported by the National Science Foundation (MCB-0314380), the National Institutes of Health (GM-30353), and the University of Connecticut Research Foundation. T.J.A. acknowledges support through the research programs ‘Physical Biology’ and ‘Biomolecular Physics’ of the Stichting voor Fundamen-teel Onderzoek der Materie (FOM) and the Stichting voor Aard en Levenswetenschappen (ALW), financially supported by the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO).
PY - 2005/11
Y1 - 2005/11
N2 - 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.
AB - 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.
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U2 - 10.1007/s11120-005-1331-8
DO - 10.1007/s11120-005-1331-8
M3 - Article
C2 - 16172929
AN - SCOPUS:25444470455
VL - 86
SP - 101
EP - 111
JO - Photosynthesis Research
JF - Photosynthesis Research
SN - 0166-8595
IS - 1-2
ER -