Data collection and refinement statistics.

Rwork and Rfree are defined by R = ∑hkl∥Fobs|−|Fcalc∥/∑hkl|Fobs|, where hkl are the indices of the reflections (used in refinement for Rwork; 5%, not used in refinement, for Rfree), and Fobs and Fcalc are the structure factors deduced from measured intensities and calculated from the model, respectively. Values in parentheses are for the highest resolution shell.