Table 1.

Data collection and refinement statistics

Data collection
Resolution, Å	20.0–1.90
Observed reflections	86,630
Unique reflections	17,326
Completeness, %	98.9 (99.1)*
Rmerge†	0.037 (0.309)*
Refinement
Protein nonhydrogen atoms	1,806
Water molecules	214
Heteroatoms (Cl−)	1
Rcryst‡	0.205 (0.239)*
Rfree‡	0.269 (0.319)*
rms deviation from ideal geometry
Bond lengths, Å	0.009
Bond angles, °	1.3
Dihedral angles, °	19.8
Average B factor, Å2	40.6

^*Values in parentheses correspond to highest resolution shell 1.93 to 1.90 Å. 

^†R_merge = ΣΣ_j|I_j(hkl) − 〈I(hkl)〉|/Σ|〈I(hkl)〉|, where I_j is the intensity measurement for reflection j and 〈I〉 is the mean intensity over j reflections. 

^‡R_cryst (R_free) = Σ∥F_obs(hkl)| − |F_calc(hkl)∥/Σ|F_obs(hkl)|, where F_obs and F_calc are observed and calculated structure factors, respectively. No σ-cutoff was applied. Ten percent of the reflections were excluded from refinement and used to calculate R_free.