TCBG Seminar

The Structure and Organization of Bacterial Photosynthetic Complexes

Professor Neil Hunter
Department of Molecular Biology and Biotechnology
University of Sheffield

Monday, July 31, 2006
3:00 pm (CT)
3269 Beckman Institute


Photosynthetic bacteria have proved to be ideal model systems for dissecting the mechanisms by which solar energy is harvested and utilized by living cells. They are easy to grow, and they have a simple photosynthetic apparatus which consists of bacteriochlorophyll-protein complexes sitting in a membrane bilayer. Two types of complex, LH2 and LH1, act as collectors and absorbers of light, and this energy passes to a reaction center (RC) complex where it is converted to a charge separation. This in turn is ultimately conserved as ATP, the chemical energy currency of all cells. The effectiveness of the LH2, LH1 and RC complexes for harvesting and utilizing solar energy depends crucially on their ability to form an interconnected macromolecular network. The seminar describes the use of atomic force microscopy (AFM) to image this network within the photosynthetic membrane from Rhodobacter sphaeroides, revealing the strategy employed by this bacterium to harvest, transmit and utilize solar energy [1]. Cryo-electron microscopy was used to determine projection structures of the purified RC- LH1-PufX and LH2 complexes at 8.5? and 6? resolution, respectively [2,3]. Together, the AFM and cryo-EM data have been used to construct a structural model of an intact photosynthetic membrane. [1] S. Bahatyrova et al., Nature 430 (2004) 1058. [2] P. Qian et al., J.Mol. Biol. 349 (2005) 948. [3] T. Walz et al., J.Mol. Biol. 282 (1998) 833.

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