PHOTOSYNTHETIC REACTION CENTERS

The reaction center is the key component for the primary events in the photochemical conversion of light into chemical energy. After excitat ion by light, a charge separation that spans the cell membrane is form ed in the reaction center in a few hundred picoseconds with a quantum yield of essentially one. A conserved pattern in the cofactors and cor e proteins of reaction centers from different organisms can be defined based on comparisons of the three dimensional structure of two types of reaction centers, Different functional aspects of the reaction cent er are discussed, including the properties of the bacteriochlorophyll or chlorophyll dimer that constitutes the primary electron donor, the pathway of electron transfer, and the different functional roles of th e electron accepters, The implication of these results on the evolutio n of the reaction center is presented. (C) 1998 Federation of European Biochemical Societies.