Table 1. Data-collection and refinement summary.

Values in parentheses are for the highest resolution shell.

Data-collection statistics
Wavelength (Å)	1.77
Space group	P212121
Unit-cell parameters (Å)	a = 93.47, b = 114.05, c = 302.52
Resolution range (Å)	49.64–2.03 (2.14–2.03)
Total No. of observations	3383622 (271866)
No. of unique reflections	198586 (26784)
Multiplicity	17.0 (10.2)
Completeness (%)	95.2 (88.9)
R merge †	0.130 (0.584)
R meas(I)‡	0.142 (0.628)
R p.i.m.(I)‡	0.034 (0.171)
〈I/σ(I)〉	25.9 (3.9)
Refinement statistics
Resolution range (Å)	49.64–2.03 (2.08–2.03)
No. of unique reflections	198460 (13278)
Completeness (%)	94.9 (86.8)
R cryst § (%)	21.3 (26.6)
R free § (%)	24.6 (30.5)
No. of protein atoms	21390
No. of heteroatoms	224
No. of water molecules	1617
Wilson B factor (Å2)	27.8
Average B factors (Å2)
Overall	31.9
Protein atoms	32.1
Water molecules	35.4
Ligand (uracil)	26.8
Potassium ions	37.1
Chloride ions	33.7
Coordinate error (ESU)	0.13
Correlation coefficient, F o − F c	0.93
Correlation coefficient, F o − F c,free	0.92
Ramachandran plot, residues in (%)
Allowed region	99.7
Disallowed region	0.30
MolProbity scores
Clashscore	1.23 [100th percentile]
Overall score	0.98 [100th percentile]

^† R _merge = .

^‡ R _meas and R _p.i.m. were calculated with SCALA (Evans, 2006 ▶) in the CCP4 suite (Winn et al., 2011 ▶) using unmerged and unscaled data pre-processed by XDS (Kabsch, 2010a ▶,b ▶). R _meas is a merging R factor independent of data redundancy, while R _p.i.m. provides the precision of the averaged measurement, which improves with higher multiplicity (Weiss, 2001 ▶). R _meas =  . R _p.i.m. =

^§The data included in the R _free set (5%) were excluded from refinement.