Table 2.

Refinement statistics

Data set	pH 4.6	pH 6.1	pH 8.3
Resolution (Å)	20–2.8	31–2.5	21–2.98
Rcrysa (%)	21.1	22.2	22.6
Rfreeb (%)	27.5	26.8	26.6
Protein residues	13–269	13–269	8–269
Protein atoms	2091	2091	2128
Non protein atoms	139	132	109
R.m.s.d. for
Bond lengths (Å)	0.007	0.006	0.007
Bond angles (°)	1.5	1.2	1.5
Dihedral angles (°)	25.6	25.7	25.9
Average B-factor (Å2)	49	53	46

^aR_crys = ∑_hkl,work ∥F_obs|− k|F_calc∥/∑_hkl|F_obs| * 100%.

^bR_free = ∑_hkl,test∥F_obs|− k|F_calc∥/∑∼_hkl|F_obs| * 100%.