Table 1. Data-collection and refinement statistics.

Values in parentheses are for the highest resolution shell.

Data collection
Resolution (Å)	50.0–2.68 (2.75–2.68)
Wavelength (Å)	0.9791
Beamline	24-ID-C, APS
Space group	P212121
Unit-cell parameters
a (Å)	59.7
b (Å)	140.1
c (Å)	143.3
No. of reflections	87487
Unique reflections	31670
Average I/σ(I)	12.2 (1.5)
Multiplicity	2.8 (1.5)
Completeness (%)	92.8 (70.0)
Rmerge† (%)	9.4 (32.9)
Data refinement
No. of protein atoms	7795
No. of ligand atoms	5
No. of water atoms	56
Working-set reflections	30019
Test-set reflections	1606
R factor‡	23.8
Rfree§	27.8
R.m.s.d. bonds (Å)	0.006
R.m.s.d. angles (°)	0.91
Mean B factor (Å2)	53
Ramachandran plot
Most favored (%)	92.7
Additionally allowed (%)	7.1
Generously allowed (%)	0.1
Disallowed (%)	0.1¶

^† R _merge = , where 〈I(hkl)〉 is the mean intensity of the i reflections with intensities I _i(hkl) and common indices hkl.

^‡ R factor = , where F _obs and F _calc are observed and calculated structure factors, respectively.

^§For R _free, the sum is extended over a subset of reflections (5%) that were excluded from all stages of refinement.

^¶Disallowed angles occurred at a Gly-Gly sequence (residues 200–201).