Correlation between structure and magnetic spin state of the manganese cluster in the oxygen-evolving complex of photosystem II in the S2 state: determination by X-ray absorption spectroscopy.
The structure of the manganese cluster in the S2 state with the g approximately 4 EPR signal (S2-g4 state) generated by 130 K illumination of photosystem II (PSII) membranes prepared from spinach has been investigated by X-ray absorption spectroscopy. The Mn X-ray absorption K-edge spectra of the S2-g4 state not only show a shift of the inflection point to higher energy from the S1 state but also reveal a different edge shape from that of the S2 state with the multiline signal (S2-MLS state). Extended X-ray absorption fine structure (EXAFS) studies of the Mn K-edge show that the structure of the Mn cluster in the S2-g4 state is distinctly different from those in the S2-MLS or S1 states. In the S2-g4 state, the second shell of back-scatters from the Mn absorber is found to contain two Mn-Mn distances of 2.73 and 2.85 A. We interpret this to indicate the presence of two nonequivalent di-mu-oxo-bridged Mn binuclear structures in the Mn cluster of the S2-g4 state. The third shell of the S2-g4 state at about 3.3 A also contains increased heterogeneity. By contrast, very little distance disorder was found to exist in the second shell of the S1 or S2-MLS states. A mechanism is proposed to explain these results in the context of our model for the Mn cluster and the EPR properties of the Mn complex in the S2 state.
Liang
W
W
Department of Chemistry, University of California, Berkeley 94720.
Latimer
M J
MJ
Dau
H
H
Roelofs
T A
TA
Yachandra
V K
VK
Sauer
K
K
Klein
M P
MP
D004578:Electron Spin Resonance Spectroscopy; D005583:Fourier Analysis; D008345:Manganese / Q000737:chemistry*; D008958:Models, Molecular; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry*; D045332:Photosystem II Protein Complex; D013057:Spectrum Analysis; D014675:Vegetables / Q000737:chemistry; D014965:X-Rays
D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D008345:Manganese