Spectroscopic Studies of Crystallized Pigment-protein Complexes of R. Palustris

Abstract

In bacterial photosynthesis, the processes of light absorption, energy migration, trapping and charge separation have been extensively studied by spectroscopic techniques using membranes and isolated antenna or reaction center (RC) complexes. With the structure of the reaction center available from high-resolution X-ray analysis, electron transport can be “visualized” and a large number of the spectroscopic data can be better understood. A similar progress in the understanding of the processes of energy migration might also be achieved with the crystallization of antenna pigment-protein complexes. Crystallization of different antenna complexes has been reported by several groups. The RC-B875 complex of the purple photosynthetic bacterium R. palustris, i.e. the reaction center with the core antenna system which is in close contact to the RC and which is synthesized in a fixed stoichiometry, has recently been crystallized by us [1]. Since this complex contains both photochemically active and inactive bacteriochlorophylls, light absorption, energy migration and charge separation may be studied. The B800–850 complex of the same bacterium has also been crystallized [2,3]. A crystal analysis of both pigment-protein complexes, at a sufficient resolution, should provide structural information that helps to understand the energetic coupling between antennae and reaction center.