The lamellar spacing in self-assembling bacteriochlorophyll aggregates is proportional to the length of the esterifying alcohol
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Chlorosomes from green photosynthetic bacteria are large photosynthetic antennae containing self-assembling aggregates of bacteriochlorophyll c, d, or e. The pigments within chlorosomes are organized in curved lamellar structures. Aggregates with similar optical properties can be prepared in vitro, both in polar as well as non-polar solvents. In order to gain insight into their structure we examined hexane-induced aggregates of purified bacteriochlorophyll c by X-ray scattering. The bacteriochlorophyll c aggregates exhibit scattering features that are virtually identical to those of native chlorosomes demonstrating that the self-assembly of these pigments is fully encoded in their chemical structure. Thus, the hexane-induced aggregates constitute an excellent model to study the effects of chemical structure on assembly. Using bacteriochlorophyllides transesterified with different alcohols we have established a linear relationship between the esterifying alcohol length and the lamellar spacing. The results provide a structural basis for lamellar spacing variability observed for native chlorosomes from different species. A plausible physiological role of this variability is discussed. The X-ray scattering also confirmed the assignments of peaks, which arise from the crystalline baseplate in the native chlorosomes.
KeywordsGreen photosynthetic bacteria Chlorosome Bacteriochlorophyll Aggregate Bacteriochlorophyllide X-ray scattering
This study was supported by Czech Ministry of Education, Youth and Sports (projects MSM0021620835, MSM6007665808, AV0Z50510513) and Czech Science Foundation (206/09/0375); R.T. was supported by Academy of Finland (project 118462) and The University of Leeds.
- Arellano JB, Melo TB, Borrego CM, Garcia-Gil J, Naqvi KR (2000) Nanosecond laser photolysis studies of chlorosomes and artificial aggregates containing bacteriochlorophyll e: evidence for the proximity of carotenoids and bacteriochlorophyll a in chlorosomes from Chlorobium phaeobacteroides strain CL1401. Photochem Photobiol 72:669–675CrossRefPubMedGoogle Scholar
- Blankenship RE, Matsuura K (2003) Antenna complexes from green photosynthetic bacteria. In: Green BR, Parson WW (eds) Light-harvesting antennas in photosynthesis, pp 195–217. Kluwer Academic Publishers, DordrechtGoogle Scholar
- Castenholz RW, Pierson BK (1995) Ecology of thermophilic anoxygenic phototrophs. In: Blankenship RE, Madigan MT, Bauer CE (eds) Anoxygenic photosynthetic bacteria, pp 87–103. Kluwer Academic Publisher, Dordrecht, The NetherlandsGoogle Scholar
- Cox RP, Miller M, Aschenbrucker J, Ma YZ, Gillbro T (1998) The role of bacteriochlorophyll e and carotenoids in light harvesting in brown-colored green sulfur bacteria. In: Garab G (ed) Photosynthesis: mechanisms and effects, vol 1. Kluwer Academic Publishers, Dordrecht, pp 149–152Google Scholar
- Miyatake T, Tamiaki H (2005) Self-aggregates of bacteriochlorophylls-c, d and e in a light-harvesting antenna system of green photosynthetic bacteria: effect of stereochemistry at the chiral 3-(1-hydroxyethyl) group on the supramolecular arrangement of chlorophyllous pigments. J Photochem Photobiol C 6:89–107CrossRefGoogle Scholar
- Vassilieva EV, Stirewalt VL, Jakobs CU, Frigaard NU, Inoue-Sakamoto K, Baker MA, Sotak A, Bryant DA (2002) Subcellular localization of chlorosome proteins in Chlorobium tepidum and characterization of three new chlorosome proteins: CsmF, CsrnH, and CsmX. Biochemistry 41:4358–4370CrossRefPubMedGoogle Scholar