Rationalizing the 1.9 Å Crystal Structure of Photosystem II—A Remarkable Jahn–Teller Balancing Act Induced by a Single Proton Transfer


  • R.S. and R.J.P. gratefully acknowledge financial assistance from the Australian Research Council. We also acknowledge the generous provision of supercomputing time on the platforms of the NCI (National Computational Infrastructure) Facility in Canberra, Australia, which is supported by the Australian Commonwealth Government. We also thank Richard Terrett for assistance in the preparation of the manuscript figures.


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Balancing act: DFT calculations show that the structures of the water-oxidizing complex in the two most recent single crystal XRD studies of photosystem II at 2.9 Å and 1.9 Å resolution are tautomers related by a single proton transfer. The anomalous oxygen species, O(5), weakly bound to four metal centers in the 1.9 Å structure (see picture) is identified as a substrate water molecule balanced between the Jahn–Teller axes of Mn(1), Mn(3), and Mn(4).