| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2001: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2000: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
The purpose of this research is to analyze genes coding for all of the subunits of oxygen-evolving photosystem (PSII) complex purified from a thermophilic cyanobacterium Thermosynechococcus vulcaus (formly Synechococcus vulcanus). We have succeeded in crystallizing the PSII complex of T vulcanus. In order to analyze the structure of PSII at atomic resolution, it is essential to know the complete composition of the complex utilized for crystallization, and the sequences of all of the subunits contained in the complex ; both of which have not been determined previously. By combining eiectrophoresis, measurement of oxygen-evolving activity, TOF-MASS measurement, and N-terminal sequencing results reported previously, we determined that there are at least 13 trans-membrane subunits and 3 extrinsic proteins existing in the PSII complex utilized for crystallization and also after crystallization. Genes for some of these components have not been cloned from T vulcanus. However, since the whole genomc sequences of another closely related thermophilic cyanobacterium T elongatLts were determined by Kazusa DNA Research Institute and will be published shortly, we focused our research on the analysis of crystal structure of PSII in the latter part of this project. By screening many heavy atom derivates, we found several derivates that yielded effective phase information ; with these information, we analysed the crystal structure of PSII at 3.7 A resolution. The resulted structure contained new information that was not available in the 3.8 A of PSII reported by Witt et al. in 2001 for PSII of T elongates. For example, the extrinsic 12 kDa protein was newly assigned in our structure, and one of the ligands to the Mn-cluster was suggested to be the C-terminal of the Dl subunits. In addition, more detailed information was obtained concerning the extrinsic loops of CP47 and CP43 that possibly protrudes into the lumenal side, the arrangements of electron transfer cofactors, etc.
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