PARENT SESSION
Posters P8B Supermolecular organization of the photosynthetic apparatus. Abstracts (592-611)

A study of the interaction between the reaction centre and light-harvesting complex I from Rhodobium marinum. Pu Qian^*,1, Per Bullough¹, Neil Hunter¹, Richard Cogdell², ¹ Department of Molecular Biology and Biotechnology, Sheffield, United Kingdom² Division of Biochemistry and Molecular Biology, Glasgow, United Kingdom

ABSTRACT- The reaction centre (RC), light-harvesting complex I (LH1) and reaction centre-light harvesting complex I (RC-LH1) complexes were isolated and purified from photosynthetic bacterium Rhodobium marinum. In order to investigate the effects caused by interaction between the RC and LH1, purified LH1 and RC-LH1 complexes were reconstituted using the lipid 1,2-diheptanoyl-sn-glycero-3-phosphocholine to form 2D crystals. In addition, absorption and CD spectra of the RC, LH1 and RC-LH1 were compared. The CD and absorption spectra of RC-LH1 were fitted using spectra of the pure RC and LH1. The experimental results show (1) that although both 2D crystals of RC-LH1 and LH1-only complexes have similar oblique symmetries, the unit cell of LH1-only complex is slightly smaller than RC-LH1, indicating that possible shrinkage of the LH1 ring takes place upon removal of the RC; (2) the absorption spectrum of the RC-LH1 can be satisfactorily fitted using spectra from the pure RC and LH1 complexes, but the CD spectrum cannot, showing that orientation of BChls in separated RC and LH1 are different from the combined one. The difference originates from interactions between BChls in the RC and LH1 complexes and between polypeptides and BChls. Further experiments are in progress.

KEY WORDS: light harvesting complex, photosynthesis, Reaction centre, supermolecular organisation