Light-Induced Structural Changes in the Primary Processes of Photosynthesis: Watching an Enzyme in Action

Continuous illumination and subsequent freezing of the crystal enabled the structure of the light-induced charge-separated state in the reaction center of a photosynthetic bacterium to be obtained by X-ray crystallography. A comparison of the position of the secondary ubiquinone cofactor Q_B in this structure (shown in gray on the right) with that in the “dark” structure (shown in black) reveals substantial motions, which are required for the subsequent electron and proton transfer processes.