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- Title
Electron transfer from Cyt b and tyrosine-D to the S and S states of the water oxidizing complex in photosystem II at cryogenic temperatures.
- Authors
Feyziyev, Yashar; Deák, Zsuzsanna; Styring, Stenbjörn; Bernát, Gábor
- Abstract
The MnCaO cluster of photosystem II (PSII) catalyzes the oxidation of water to molecular oxygen through the light-driven redox S-cycle. The water oxidizing complex (WOC) forms a triad with Tyrosine and P, which mediates electrons from water towards the acceptor side of PSII. Under certain conditions two other redox-active components, Tyrosine (Y) and Cytochrome b (Cyt b) can also interact with the S-states. In the present work we investigate the electron transfer from Cyt b and Y to the S and S states at 195 K. First, Y and Cyt b were chemically reduced. The S and S states were then achieved by application of one or two laser flashes, respectively, on samples stabilized in the S state. EPR signals of the WOC (the S-state multiline signal, ML-S), Y and oxidized Cyt b were simultaneously detected during a prolonged dark incubation at 195 K. During 163 days of incubation a large fraction of the S population decayed to S in the S samples by following a single exponential decay. Differently, S samples showed an initial increase in the ML-S intensity (due to S to S conversion) and a subsequent slow decay due to S to S conversion. In both cases, only a minor oxidation of Y was observed. In contrast, the signal intensity of the oxidized Cyt b showed a two-fold increase in both the S and S samples. The electron donation from Cyt b was much more efficient to the S state than to the S state.
- Subjects
CHARGE exchange reactions; TYROSINE; PHOTOSYSTEMS; OXIDATION of water; TEMPERATURE effect; MANGANESE compounds; CYTOCHROME b; ELECTRON paramagnetic resonance spectroscopy
- Publication
Journal of Bioenergetics & Biomembranes, 2013, Vol 45, Issue 1/2, p111
- ISSN
0145-479X
- Publication type
Article
- DOI
10.1007/s10863-012-9482-8