Abstract
The crystal structure of photosystem II (PSII) has been reported from three groups including the author's group; based on these structural models, a number of new functional features of PSII have been revealed or suggested. The resolution of PSII structure reported so far, however, was at around 3.5 A, which is apparently not high enough to reveal the detailed structure of amino acid side chains as well as that of the Mn cluster. In order to improve the crystal quality, we improved the preparation procedure and crystallization conditions of PSII from the thermophilic cyanobacterium, Thermosynechococcus vulcanus. In addition, we optimized the cryogenic conditions for X-ray experiments, which allowed us to collect diffraction data set from PSII crystals at a 3.3 A resolution. We modified the PSII structure using the improved diffraction data, and will discuss PSII functions based on our recent structural model, together with prospects on PSII structure analysis.
