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Light-induced structural changes in phot ... ism of electron-proton transfer
Light-induced structural changes in photosynthetic reaction center: implications for mechanism of electron-proton transfer.
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High resolution x-ray diffraction data from crystals of the Rhodobacter sphaeroides photosynthetic reaction center (RC) have been collected at cryogenic temperature in the dark and under illumination, and the structures were refined at 2.2 and 2.6 angstrom resolution, respectively. In the charge-separated D+QAQB- state (where D is the primary electron donor (a bacteriochlorophyll dimer), and QA and QB are the primary and secondary quinone acceptors, respectively), QB- is located approximately 5 angstroms from the QB position in the charge-neutral (DQAQB) state, and has undergone a 180 degrees propeller twist around the isoprene chain. A model based on the difference between the two structures is proposed to explain the observed kinetics of electron transfer from QA-QB to QAQB- and the relative binding affinities of the different ubiquinone species in the QB pocket. In addition, several water channels (putative proton pathways) leading from the QB pocket to the surface of the RC were delineated, one of which leads directly to the membrane surface.
Stowell MH, McPhillips TM, Rees DC, Soltis SM, Abresch E, Feher G
Science (New York, N.Y.)
1997-05-02 00:00
276
5313
812-6
Binding Sites,Cell Membrane,Crystallization,Crystallography, X-Ray,Darkness,Electron Transport,Freezing,Hydrogen Bonding,Light,Light-Harvesting Protein Complexes,Models, Molecular,Photosynthetic Reaction Center Complex Proteins,Protein Conformation,Protons,Rhodobacter sphaeroides,Temperature,Ubiquinone,Light-Harvesting Protein Complexes,Photosynthetic Reaction Center Complex Proteins,Protons,Ubiquinone
Division of Chemistry and Chemical Engineering, 147-75CH, California Institute of Technology, Pasadena, CA 91125, USA
Science
NIGMS GM13191, NIGMS GM45162
0036-8075
1105
True
9115209
