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

Fujii, R., Shimonaka, S., Uchida, N., Gardiner, A.T., Cogdell, R.J. , Sugisaki, M. and Hashimoto, H. (2008) 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. Photosynthesis Research, 95(2-3), pp. 327-337. (doi:10.1007/s11120-007-9260-3)

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Publisher's URL: http://dx.doi.org/10.1007/s11120-007-9260-3

Abstract

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. (<i>2005</i>) 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 <i>Rhodopseudomonas acidophila</i>) and LH1-RC (from <i>Rhodopseudomonas viridis</i>) 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 <i>a</i>, and the core complexes contain bacteriochlorophyll <i>b</i>, 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.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Cogdell, Professor Richard
Authors: Fujii, R., Shimonaka, S., Uchida, N., Gardiner, A.T., Cogdell, R.J., Sugisaki, M., and Hashimoto, H.
Subjects:Q Science > QK Botany
College/School:College of Medical Veterinary and Life Sciences > Institute of Molecular Cell and Systems Biology
Journal Name:Photosynthesis Research
Publisher:Springer
ISSN:0166-8595
Published Online:10 October 2007

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
303032The structure and function of purple bacterial antenna complexesRichard CogdellBiotechnology and Biological Sciences Research Council (BBSRC)BB/D000610/1Institute of Molecular Cell and Systems Biology