Spectroscopic properties and chromophore conformations of the photomorphogenic receptor: Phytochrome |
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| Affiliation: | 1. Department of Agronomy, Faculty of Agriculture, Universitas Padjadjaran, Bandung, Indonesia;2. Plantation Seed Supervision and Certification Center, Bandung, Indonesia;3. Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan;4. Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan;5. Tsukuba Plant Innovation Research Center, University of Tsukuba, Tsukuba, Japan;1. Department of Physics and Astronomy, Faculty of Science, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands;2. Department of Biology, Northeastern Illinois University, 5500 N. St. Louis Ave., Chicago, IL 60625, USA;1. Metallurgical and Materials Engineering Department, The University of Texas at El Paso, 500 West University Ave., El Paso, TX, USA;2. Department of Chemistry, The University of Texas at El Paso, 500 West University Avenue, El Paso, TX 79968, USA;3. University of California Center for Environmental Implications of Nanotechnology (UC CEIN), The University of Texas at El Paso, El Paso, TX, USA;4. Department of Environmental Geosciences, Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21, Prague 6 – Suchdol, Czech Republic;5. State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing 210046, China;6. Environmental Science and Engineering PhD Program, The University of Texas at El Paso, 500 West University Avenue, El Paso, TX 79968, USA;7. Department of Chemistry, University of Puerto Rico at Mayagu¨ez, Mayagu¨ez, PR 00680, USA;1. State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing 210046, China;2. Department of Chemistry, The University of Texas, El Paso, TX 79968, United States;3. Environmental Science and Engineering Ph.D. Program, The University of Texas at El Paso, El Paso, TX 79968, United States;4. University of California Center for Environmental Implications of Nanotechnology (UC CEIN), The University of Texas at El Paso, El Paso, TX 79968, United States;1. Faculty of Chemistry, University of Wrocław, 14 F. Joliot-Curie str., 50-383 Wrocław, Poland;2. Faculty of Chemistry and Chemical Technology, University of Ljubljana, Vecna Pot 113, SI-1000 Ljubljana, Slovenia;1. Department of Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR 97331-4003, United States;2. Graduate School of Integrated Science and Technology, Shizuoka University, 422-8529 Shizuoka, Japan;3. Graduate School of Arts and Sciences, University of Tokyo, 153-8902 Tokyo, Japan;4. Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency, 332-0012 Saitama, Japan |
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| Abstract: | Fluorescence lifetimes of ‘large’ (mol. wt. 120 000) and ‘small’ (mol. wt. 60 000) phytochromes isolated from oat and rye seedlings grown in the dark have been measured at 199 K and 298 K. Phytochrome model compounds have also been studied by phase modulation fluorometrically at 77 K for comparison with lifetime data for phytochrome. It was found that the fluorescence lifetime of ‘large’ phytochrome was significantly shorter than that of ‘small’ phytochrome and its chromophore models. The phytochrome chromophore of Pr form has been analyzed by fluorescence polarization, CD, and molecular orbital methods. The fluorescence excitation polarization of ‘small’ phytochrome and the chromophore model in buffer/glycerol mixture (3 : 1, v/v) at 77 K is very high (0.4) at the main absorption band and is negative (−0.1) and close to 0 in the near ultraviolet band, respectively. Analyses of the spectroscopic data suggest that the chromophore conformation of Pr and Pfr forms of phytochrome are essentially identical. The induced ellipticity of ‘large’ rye phytochrome in the blue and near ultraviolet regions was found to be significantly higher than that of ‘small’ phytochrome, indicating that the binding interaction between the phytochrome chromophore and apoprotein is much tighter in the former than in the latter. In addition, the excitation energy transfer does occur from Trp residue(s) to the chromophore in ‘large’ phytochrome but not in ‘small’ Pr. This illustrates one feature of the role played by the large molecular weight apoprotein in the binding site interactions and primary photoprocesses of Pr. Finally, a plausible model for the primary photoprocesses and the mechanism of phytochrome interactions triggered by the Pr → Pfr phototransformation have been proposed on the basis of the above results. |
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