Summary of crystal parameters, data collection, and refinement statistics.

*Rmerge = ∑h ∑i | Ii (h)−|/∑h∑i Ii(h), where Ii(h) is the intensity of an individual measurement of the reflection and is the mean intensity of the reflection. §Rcryst = ∑h ||Fobs|−|Fcalc||/∑h |Fobs|, where Fobs and Fcalc are the observed and calculated structure-factor amplitudes, respectively. ¶Rfree was calculated as Rcryst using 1.5% of randomly selected unique reflections that were omitted from the structure refinement. Values in parentheses are for the highest resolution shell.