Data Collection and Refinement Statistics.

Data for the highest-resolution shell are given in parentheses.Rmerge = ΣhΣi|Ih,i − ⟨Ih⟩|/ΣhΣiIh,i, where the outer sum (h) is over the unique reflections and the inner sum (i) is over the set of independent observations of each unique reflection.Rwork = ∑hkl||Fobs| − |Fcalc||/∑Fobs, where Fobs and Fcalc are the observed and calculated structure factors of the respective reflections hkl.Rfree is equivalent to Rwork but is calculated on a random set of reflections corresponding to 5% of all reflections and that are excluded from refinement.*As defined by MolProbity [52]Data Collection and Refinement Statistics.