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Flash-induced relax...
Flash-induced relaxation changes of the EPR signals from the manganese cluster and YD reveal a light-adaptation process of Photosystem II
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- Peterson Årsköld, Sindra (författare)
- Lund University,Lunds universitet,Biokemi och Strukturbiologi,Centrum för Molekylär Proteinvetenskap,Kemiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Biochemistry and Structural Biology,Center for Molecular Protein Science,Department of Chemistry,Departments at LTH,Faculty of Engineering, LTH
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Åhrling, Karin A (författare)
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- Högblom, Joakim (författare)
- Lund University,Lunds universitet,Biokemi och Strukturbiologi,Centrum för Molekylär Proteinvetenskap,Kemiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Biochemistry and Structural Biology,Center for Molecular Protein Science,Department of Chemistry,Departments at LTH,Faculty of Engineering, LTH
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- Styring, Stenbjörn (författare)
- Lund University,Lunds universitet,Biokemi och Strukturbiologi,Centrum för Molekylär Proteinvetenskap,Kemiska institutionen,Institutioner vid LTH,Lunds Tekniska Högskola,Biochemistry and Structural Biology,Center for Molecular Protein Science,Department of Chemistry,Departments at LTH,Faculty of Engineering, LTH
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(creator_code:org_t)
- 2003-02-12
- 2003
- Engelska.
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 0006-2960 .- 1520-4995. ; 42:9, s. 2748-2758
- Relaterad länk:
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http://dx.doi.org/10...
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https://lup.lub.lu.s...
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https://doi.org/10.1...
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Abstract
Ämnesord
Stäng
- By exposing photosystem II (PSII) samples to an incrementing number of excitation flashes at room temperature, followed by freezing, we could compare the Mn-derived multiline EPR signal from the S-2 oxidation state as prepared by 1, 5, 10, and 25 flashes of light. While the S-2 multiline signals exhibited by these samples differed very little in spectral shape, a significant increase of the relaxation rate of the signal was detected in the multiflash samples as compared to the S-2-state produced by a single oxidation. A similar relaxation rate increase was observed for the EPR signal from Y-D(.). The temperature dependence of the multiline spin-lattice relaxation rate is similar after 1 and 5 flashes. These data are discussed together with previously reported phenomena in terms of a light-adaptation process of PSII, which commences on the third flash after dark-adaptation and is completed after 10 flashes. At room temperature, the fast-relaxing, light-adapted state falls back to the slow-relaxing, dark-adapted state with t(1/2) = 80 s. We speculate that light-adaptation involves changes necessary for efficient continuous water splitting. This would parallel activation processes found in many other large redox enzymes, such as Cytochrome c oxidase and Ni-Fe hydrogenase. Several mechanisms of light-adaptation are discussed, and we find that the data may be accounted for by a change of the PSII protein matrix or by the light-induced appearance of a paramagnetic center on the PSII donor side. At this time, no EPR signal has been detected that correlates with the increase of the relaxation rates, and the nature of such a new paramagnet remains unclear. However, the relaxation enhancement data could be used, in conjunction with the known Mn-Y-D distance, to estimate the position of such an unknown relaxer. If positioned between Y-D and the Mn cluster, it would be located 7-8 Angstrom from the spin center of the S-2 multiline signal.
Ämnesord
- NATURVETENSKAP -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)
- NATURAL SCIENCES -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)
Nyckelord
- MULTILINE SIGNAL
- SATURATION-RECOVERY EPR
- SPIN-LATTICE RELAXATION
- PHOTOSYNTHETIC O2 EVOLUTION
- OXYGEN-EVOLVING COMPLEX
- S-2 STATE
- ELECTRON-PARAMAGNETIC-RESONANCE
- IRON-SULFUR PROTEINS
- DYSPROSIUM COMPLEXES
- INDUCED ENHANCEMENTS
Publikations- och innehållstyp
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- ref (ämneskategori)
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