Control Mechanism of Excitation Energy Transfer in a Complex Consisting of Photosystem II and Fucoxanthin Chlorophyll a/c-Binding Protein.
Fucoxanthin chlorophyll (Chl) a/c-binding protein (FCP) is a unique light-harvesting antenna in diatoms, which are photosynthesizing algae ubiquitous in aquatic environments. However, it is unknown how excitation energy is trapped and quenched in a complex consisting of photosystem II and FCP (PSII-FCPII complex). Here, we report the control mechanism of excitation energy transfer in the PSII-FCPII complexes isolated from a diatom, Chaetoceros gracilis, as revealed by picosecond time-resolved fluorescence spectroscopy. The results showed that Chl-excitation energy is harvested in low-energy Chls near/within FCPII under the 77 K conditions, whereas most of the energy is trapped in reaction center Chls in PSII under the 283 K conditions. Surprisingly, excitation energy quenching was observed in a part of PSII-FCPII complexes with the time constants of hundreds of picosecond, thus indicating the large contribution of FCPII to energy trapping and quenching. On the basis of these results, we discuss the light-harvesting strategy of diatoms.
†Division of Material Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
Ryo
R
Nagao
‡Molecular Photoscience Research Center, Kobe University, Kobe 657-8501, Japan.
Makio
M
Yokono
§Department of Biology, Faculty of Science, Tokyo University of Science, Kagurazaka 1-3, Shinjuku-ku, Tokyo 162-8601, Japan.|∥PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan.
Tatsuya
T
Tomo
‡Molecular Photoscience Research Center, Kobe University, Kobe 657-8501, Japan.|⊥JST, CREST, Kobe 657-8501, Japan.
Seiji
S
Akimoto
FDAS; TRFS; diatom; low light; low-energy Chl