Abstract
Diatoms are unicellular algae found throughout the world,s ocean and freshwater, and one of the most important algae in aquatic ecosystems and the global carbon cycles. Photosynthesis by marine diatoms is predicted to be comparable to that of all terrestrial rain forests. In spite of their significance, little is known about Photosystem 2 (PS2) in diatoms. Isolation of diatom PS2 have been blocked at the level of obtaining thylakoid membranes that are capable of oxygen evolution, because it is difficult to break silica-based rigid cell-wall. In this study, we found that diatom cells were readily disrupted by freeze-thaw, and succeeded in preparation of thylakoid membranes retaining high oxygen-evolving activity. Furthermore, diatom PSII particles were prepared by centrifugation of Triton X-100 extracts of the thylakoid membranes. The diatom PSII particles contained five extrinsic proteins, PsbO, PsbQ,, PsbV, hypothetical protein and PsbU. We will report about various properties of the diatom PS2.
