Energy dissipation efficiency in the CP43 assembly intermediate complex of photosystem II |
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| Institution: | 1. Department of Biology, Washington University, St. Louis, MO 63130, USA;2. Center for Solar Energy and Energy Storage, Washington University, St. Louis, MO 63130, USA;3. Department of Energy, Environmental & Chemical Engineering, Washington University, St. Louis, MO 63130, USA;1. Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, IL 60439, United States;2. Photon Sciences Directorate, Argonne National Laboratory, Lemont, IL 60439, United States;1. Institute of Biological Chemistry, Washington State University, Pullman, WA, USA;2. Department of Biochemistry and Center for Plant Biology, Purdue University, West Lafayette, IN 47907, USA;1. A.N. Belozersky Institute of Physical-Chemical Biology, Moscow State University, 119992 Moscow, Leninskie Gory, 1, Building 40, Russia;2. .;1. Life Science Research Infrastructure Group, RIKEN SPring-8 Center, Kouto, Hyogo, Japan;2. Laboratory for Protein Crystallography, Institute for Protein Research, Osaka University, Suita, Osaka, Japan;3. Faculty of Science, Department of Science, Yamagata University, Yamagata, Japan;4. National Institute for Basic Biology, National Institutes of Natural Sciences, Okazaki, Japan;5. Chemistry Research Laboratory, South Parks Road, Oxford University, United Kingdom;6. Cellular and Structural Physiology Institute, Nagoya University, Nagoya, Japan;7. Graduate School of Pharmaceutical Sciences, Nagoya University, Nagoya, Japan;8. Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, Ibaraki, Osaka, Japan;9. Department of Basic Biology, School of Life Science, the Graduate University for Advanced Studies, Sokendai, Okazaki, Japan |
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| Abstract: | Photosystem II in oxygenic organisms is a large membrane bound rapidly turning over pigment protein complex. During its biogenesis, multiple assembly intermediates are formed, including the CP43-preassembly complex (pCP43). To understand the energy transfer dynamics in pCP43, we first engineered a His-tagged version of the CP43 in a CP47-less strain of the cyanobacterium Synechocystis 6803. Isolated pCP43 from this engineered strain was subjected to advanced spectroscopic analysis to evaluate its excitation energy dissipation characteristics. These included measurements of steady-state absorption and fluorescence emission spectra for which correlation was tested with Stepanov relation. Comparison of fluorescence excitation and absorptance spectra determined that efficiency of energy transfer from β-carotene to chlorophyll a is 39 %. Time-resolved fluorescence images of pCP43-bound Chl a were recorded on streak camera, and fluorescence decay dynamics were evaluated with global fitting. These demonstrated that the decay kinetics strongly depends on temperature and buffer used to disperse the protein sample and fluorescence decay lifetime was estimated in 3.2–5.7 ns time range, depending on conditions. The pCP43 complex was also investigated with femtosecond and nanosecond time-resolved absorption spectroscopy upon excitation of Chl a and β-carotene to reveal pathways of singlet excitation relaxation/decay, Chl a triplet dynamics and Chl a → β-carotene triplet state sensitization process. The latter demonstrated that Chl a triplet in the pCP43 complex is not efficiently quenched by carotenoids. Finally, detailed kinetic analysis of the rise of the population of β-carotene triplets determined that the time constant of the carotenoid triplet sensitization is 40 ns. |
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