2006 Fiscal Year Final Research Report Summary
Photoacclimation of photosynthetic light-harvesting systems
| Project/Area Number |
17570029
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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・分子
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| Research Institution | Hokkaido University |
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Principal Investigator |
MINAGAWA Jun Hokkaido Univ., Inst. of Low Temp. Sci., Asso. Prof., 低温科学研究所, 助教授 (80280725)
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| Project Period (FY) |
2005 – 2006
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| Keywords | photosynthesis / green algae / acclimation / light-harvesting system |
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| Research Abstract |
State transition in photosynthesis is a short-term balancing mechanism of energy distribution between photosystem I (PSI) and photosystem II (PSII). When PSII is preferentially excited (State 2), a pool of mobile light-harvesting complex II (LHCII) antenna proteins is thought to migrate from PSII to PSI, but biochemical evidence for a physical association between LHCII proteins and PSI in State 2 is weak. Here, using the green alga Chlamydomonas reinhardtii, which has a high capacity for state transitions, we report the isolation of PSI-LHCI supercomplexes from cells locked into State 1 and State 2. We solubilized the thylakoid membranes with a mild detergent, separated the proteins by sucrose density gradient centrifugation, and subjected gradient fractions to gel filtration chromatography. Three LHCII polypeptides were associated with a PSI-LHCI supercomplex only in State 2; we identified them as two minor monomeric LHCII proteins (CP26 and CP29) and one previously unreported major LHCII protein Type II, or LhcbM5. These three LHCII proteins, in addition to the major trimeric LHCII proteins, were phosphorylated upon transition to State 2. The corresponding phylogenetic tree indicates that among the LHCII proteins associated with PSII, these are most similar to the LHC proteins for PSI (LHCI). Our results are important because CP26,CP29, and LhcbM5, which have been viewed as belonging solely to the PSII complex, are now postulated to shuttle between PSI and PSII during state transitions, thereby acting as docking sites for the trimeric LHCII proteins in both PSI and PSII.
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Research Products
(14 results)
