| Project/Area Number |
26840023
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| Research Category |
Grant-in-Aid for Young Scientists (B)
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| Allocation Type | Multi-year Fund |
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| Research Field |
Structural biochemistry
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| Research Institution | Okayama University |
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Principal Investigator |
Suga Michi 岡山大学, 自然科学研究科, 助教 (60634920)
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| Project Period (FY) |
2014-04-01 – 2016-03-31
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| Project Status |
Completed (Fiscal Year 2015)
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| Budget Amount *help |
¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000)
Fiscal Year 2015: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2014: ¥3,510,000 (Direct Cost: ¥2,700,000、Indirect Cost: ¥810,000)
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| Keywords | 光化学系II / 膜タンパク質 / 光合成 / 結晶構造解析 / X線自由電子レーザー / 無損傷 / 光化学系II複合体 / XFEL |
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| Outline of Final Research Achievements |
The initial reaction of photosynthesis takes place in photosystem II (PSII), a 700 kDa membrane protein complex that catalyzes water-splitting reaction through an S-state cycle of the oxygen evolving complex (OEC). The structure of PSII has been solved by XRD at 1.9 A resolution, which revealed that the OEC is a Mn4CaO5 cluster. However, the manganese atoms in the OEC are easily reduced by X-ray irradiation.
Recently, it was demonstrated that radiation damage free structure can be obtainable using X-ray free electron lasers (XFEL). We determined a radiation damage free structure of PSII in the S1 state at a resolution of 1.95 A using XFEL pulses. Compared with the structure from XRD, the OEC in the XFEL structure has Mn-Mn distances that are shorter by 0.1-0.2A. Based on the XFEL structure, the valences of each manganese atom were assigned as Mn1(+3), Mn2(+4), Mn3(+4) and Mn4(+3) in the S1 state. These findings provide a structural basis for the mechanism of oxygen evolution.
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