Abstract
Red alga is one of the eukaryotic algae closely related to cyanobacteria, but its PSII differs from that of cyanobacteria in that the former contains a PsbQ', the fourth extrinsic protein. The crystal structure of PSII from cyanobacteria has been reported at 2.9 angstrom resolution; however, no reports have been published on the structure of any eukaryotic PSII. In order to elucidate the structure of red algal PSII, we have been purifying and crystallizing PSII from a red alga Cyanidium caldarium, and have succeeded in obtaining crystals diffracting to 3.5 angstrom resolution(Adachi H., Umena Y., Enami I., Henmi T.,Kamiya N., Shen J-R.(2009) Biochim. Biophys. Acta. 1787, 121-128). To improve the resolution of the red algal PSII crystals, we modified the purification procedure of PSII and the conditions for post-crystallization dehydration. As a result, crystals diffracting to a 2.9 angstrom resolution was obtained. This resolution would allow us to elucidate more detailed structure of the red algal PSII.
