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Crystal structure of photosystem II from Synechococcus elongatus at 3.8 Å resolution


Oxygenic photosynthesis is the principal energy converter on earth. It is driven by photosystems I and II, two large protein–cofactor complexes located in the thylakoid membrane and acting in series. In photosystem II, water is oxidized; this event provides the overall process with the necessary electrons and protons, and the atmosphere with oxygen. To date, structural information on the architecture of the complex has been provided by electron microscopy of intact, active photosystem II at 15–30 Å resolution1, and by electron crystallography on two-dimensional crystals of D1-D2-CP47 photosystem II fragments without water oxidizing activity at 8 Å resolution2. Here we describe the X-ray structure of photosystem II on the basis of crystals fully active in water oxidation3. The structure shows how protein subunits and cofactors are spatially organized. The larger subunits are assigned and the locations and orientations of the cofactors are defined. We also provide new information on the position, size and shape of the manganese cluster, which catalyzes water oxidation.

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Figure 1: Electron densities of PSII after density modification and their interpretation.
Figure 2: Structure of PSII with assignment of protein subunits and cofactors.
Figure 3: Arrangement of cofactors of the electron transfer chain located in subunits D1 and D2.
Figure 4: Location and orientation of manganese cluster.


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We thank C. Lüneberg, H. Schmidt and D. DiFiore for technical assistance, and W.-D. Schubert, R. Bittl, E. Schlodder, K. Irrgang and P. Jordan for discussions. Beamline assistance at DESY (Hamburg), ESRF (Grenoble) and Elettra (Trieste), and help of M. Burghammer with data collection at the manganese edge is gratefully acknowledged. We thank Egbert J. Boekema for providing us with electron micrographs of PSII. This work was supported by Deutsche Forschungsgemeinschaft, Sonderforschungsbereiche 312 and 498, BMBF (W.S.), and Fonds der Chemischen Industrie (W.S., H.-T.W., N.K. and P.F.).

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Correspondence to Wolfram Saenger.

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Zouni, A., Witt, HT., Kern, J. et al. Crystal structure of photosystem II from Synechococcus elongatus at 3.8 Å resolution. Nature 409, 739–743 (2001).

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