Construction of hybrid photosynthetic units using peripheral and core antennae from two different species of photosynthetic bacteria: detection of the energy transfer from bacteriochlorophyll a in LH2 to bacteriochlorophyll b in LH1
| Autor: | Hideki Hashimoto, Alastair T. Gardiner, Shozo Shimonaka, Mitsuru Sugisaki, Richard J. Cogdell, Naoko Uchida, Ritsuko Fujii |
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| Rok vydání: | 2007 |
| Předmět: |
Light-Harvesting Protein Complexes
macromolecular substances Plant Science Biology Photochemistry Photosynthesis Biochemistry Light-harvesting complex chemistry.chemical_compound Microscopy Electron Transmission Lipid bilayer Bacteriochlorophylls Bacteriochlorophyll A Cell Biology General Medicine Rhodopseudomonas Crystallography Spectrometry Fluorescence Membrane Energy Transfer chemistry Orthorhombic crystal system Photosynthetic membrane Bacteriochlorophyll Photosynthetic bacteria |
| Zdroj: | Photosynthesis Research. 95:327-337 |
| ISSN: | 1573-5079 0166-8595 |
| DOI: | 10.1007/s11120-007-9260-3 |
| Popis: | Typical purple bacterial photosynthetic units consist of supra-molecular arrays of peripheral (LH2) and core (LH1-RC) antenna complexes. Recent atomic force microscopy pictures of photosynthetic units in intact membranes have revealed that the architecture of these units is variable (Scheuring et al. (2005) Biochim Bhiophys Acta 1712:109-127). In this study, we describe methods for the construction of heterologous photosynthetic units in lipid-bilayers from mixtures of purified LH2 (from Rhodopseudomonas acidophila) and LH1-RC (from Rhodopseudomonas viridis) core complexes. The architecture of these reconstituted photosynthetic units can be varied by controlling ratio of added LH2 to core complexes. The arrangement of the complexes was visualized by electron-microscopy in combination with Fourier analysis. The regular trigonal array of the core complexes seen in the native photosynthetic membrane could be regenerated in the reconstituted membranes by temperature cycling. In the presence of added LH2 complexes, this trigonal symmetry was replaced with orthorhombic symmetry. The small lattice lengths for the latter suggest that the constituent unit of the orthorhombic lattice is the LH2. Fluorescence and fluorescence-excitation spectroscopy was applied to the set of the reconstituted membranes prepared with various proportions of LH2 to core complexes. Remarkably, even though the LH2 complexes contain bacteriochlorophyll a, and the core complexes contain bacteriochlorophyll b, it was possible to demonstrate energy transfer from LH2 to the core complexes. These experiments provide a first step along the path toward investigating how changing the architecture of purple bacterial photosynthetic units affects the overall efficiency of light-harvesting. |
| Databáze: | OpenAIRE |
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