Density functional theory calculated N hyperfine couplings are obtained for the Mn1 ligated π-N of residue His332 of the photosystem 2 water oxidizing complex. An open cubane, O4H, model closely matches the experimental coupling obtained for the high spin = 5/2 form of the S state, supporting an open cubane structure for this state. We also investigate the unusual geometric features for the S state obtained by X-ray free electron laser structure determinations and rationalize it as an equilibrium occurring at room temperature between W1/O4 deprotonated and protonated forms of the open cubane structure.