Structural basis of bacterial photosynthetic reaction centers

The photosynthetic reaction center (RC) is the first membrane protein whose three-dimensional structure was revealed at the atomic level by X-ray crys tallograph more than fifteen years ago. Structural information about RC mad e a great contribution to the understanding of the reaction mechanism of th e complicated membrane protein complex. High-resolution structures of RCs f rom three photosynthetic bacteria are now available, namely, those from two mesophilic purple non-sulfur bacteria, Blastochloris viridis and Rhodobact er sphaeroides, and that from a thermophilic purple sulfur bacterium, Therm ochromatium tepidum. In addition, a variety of structural studies, mainly b y X-ray crystallography, are still being performed to give more detailed in sight into the reaction mechanism of this membrane protein. This review dea ls with structural studies of bacterial RC complexes, and a discussion abou t the electron transfer reaction between RCs and electron donors is the mai n focus out of several topics addressed by these structural studies. The st ructural data from three RCs and their electron donors provided reliable mo dels for molecular recognition in the primary step of bacterial photosynthe sis.