Glycolipid analyses of light-harvesting chlorosomes from envelope protein mutants of Chlorobaculum tepidum
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Chlorosomes are large and efficient light-harvesting organelles in green photosynthetic bacteria, and they characteristically contain large numbers of bacteriochlorophyll c, d, or e molecules. Self-aggregated bacteriochlorophyll pigments are surrounded by a monolayer envelope membrane comprised of glycolipids and Csm proteins. Here, we analyzed glycolipid compositions of chlorosomes from the green sulfur bacterium Chlorobaculum tepidum mutants lacking one, two, or three Csm proteins by HPLC equipped with an evaporative light-scattering detector. The ratio of monogalactosyldiacylglyceride (MGDG) to rhamnosylgalactosyldiacylglyceride (RGDG) was smaller in chlorosomes from mutants lacking two or three proteins in CsmC/D/H motif family than in chlorosomes from the wild-type, whereas chlorosomes lacking CsmIJ showed relatively less RGDG than MGDG. The results suggest that the CsmC, CsmD, CsmH, and other chlorosome proteins are involved in organizing MGDG and RGDG and thereby affect the size and shape of the chlorosome.
KeywordsBacteriochlorophyll Chlorosome Glycolipid Green sulfur bacteria Photosynthesis
Evaporative light-scattering detector
Green sulfur bacteria
This work was partially supported by Grants-in-Aid for Scientific Research (A) (No. 22245030 to H.T.), for Scientific Research (C) (No. 24550065 to T.M.), for Young Scientists (B) (No. 26840099 to Y.T.), and for Scientific Research on Innovative Areas (“Artificial Photosynthesis,” No. 24107002 to H.T.) from the Japan Society for the Promotion of Science (JSPS). This work was also supported by the PRESTO (Precursory Research for Embryonic Science and Technology) program from the Japan Science and Technology Agency (JST). Work in the laboratory of D. A. B. was supported by grant DE-FG02-94ER20137 from the U. S. Department of Energy.
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