Photosynthesis. Electronic structure of the oxygen-evolving complex in photosystem II prior to O-O bond formation

Science. 2014 Aug 15;345(6198):804-8. doi: 10.1126/science.1254910. Epub 2014 Aug 14.


The photosynthetic protein complex photosystem II oxidizes water to molecular oxygen at an embedded tetramanganese-calcium cluster. Resolving the geometric and electronic structure of this cluster in its highest metastable catalytic state (designated S3) is a prerequisite for understanding the mechanism of O-O bond formation. Here, multifrequency, multidimensional magnetic resonance spectroscopy reveals that all four manganese ions of the catalyst are structurally and electronically similar immediately before the final oxygen evolution step; they all exhibit a 4+ formal oxidation state and octahedral local geometry. Only one structural model derived from quantum chemical modeling is consistent with all magnetic resonance data; its formation requires the binding of an additional water molecule. O-O bond formation would then proceed by the coupling of two proximal manganese-bound oxygens in the transition state of the cofactor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism
  • Chemical Phenomena
  • Cyanobacteria / chemistry*
  • Cyanobacteria / metabolism
  • Electron Spin Resonance Spectroscopy
  • Magnetic Resonance Spectroscopy
  • Manganese / chemistry
  • Models, Chemical
  • Oxidation-Reduction
  • Oxygen / chemistry*
  • Oxygen / metabolism
  • Photosynthesis
  • Photosystem II Protein Complex / chemistry*
  • Photosystem II Protein Complex / metabolism
  • Water / chemistry


  • Bacterial Proteins
  • Photosystem II Protein Complex
  • Water
  • Manganese
  • Oxygen