1999 Fiscal Year Final Research Report Summary
Mechanism of the action of active oxygen species and proteases in the degradation of photosystem II complexes
| Project/Area Number |
10640634
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
植物生理
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| Research Institution | OKAYAMA UNIVERSITY |
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Principal Investigator |
YAMAMOTO Yasusi Okayama Univ., Dept. Biol., Professor, 理学部, 教授 (40091251)
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| Project Period (FY) |
1998 – 1999
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| Keywords | Photosynthesis / Photoinhibition / DI protein / Active oxygen / Protease / Turnover |
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| Research Abstract |
When chloroplasts are illuminated with strong light, the reaction-center binding D1 protein of photosystem II (PS II) Is damaged and degraded. In the protein degradation, active oxygen molecules produced at the acceptor-side of PS II and the endogenous cationic radicals generated at the donor-side of PS II are involved. It was also shown that the extrinsic proteins of PS II (OEC subunits) play s regulatory role in the degradation of the D1 protein. In the present study, we analyzed the action of the oxygen- and cationic radicals on the degradation of the D1 protein. We also studied the secondary structure of the OEC subunits. The results are summarized below.
(1) Photodamaged D1 protein easily cross-links with the surrounding polypeptides in PS II. We found that the cross-linked products are not the dead-end products, but are digested by a stromal protease(s). The protease(s) is SDS-resistant. A 15-kDa factor in the stroma was found to have the protease activity.
(2) Among the cross-linked products, generation of those between the D1 protein and CP43 were shown to be regulated by the OEC33. These results suggest that the OEC subunit plays a molecular chaperone-like role.
(3) The secondary structures of OEC24 and OEC18 were analyzed by Fourier transform infrared spectroscopy. The results obtained show that these proteins have a large amount of β-sheet structure and they are relatively stable to heat treatment.
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