Table 1. Summary of data-collection and refinement statistics.

Values in parentheses are for the highest resolution shell.

	Zinc-bound crystal
	1st crystal
	Zn edge	Zn peak	Zn remote	2nd crystal	Zinc-free iron-bound crystal
Data collection
Wavelength (Å)	1.2829	1.2822	1.0000	1.0000	1.0000
Resolution range (Å)	50.0–2.40 (2.49–2.40)			50.0–2.20 (2.28–2.20)	50.0–2.80 (2.90–2.80)
No. of observed reflections	125496	136427	139258	125281	69903
No. of unique reflections	36071	37010	37531	26551	12243
Data completeness (%)	96.6 (74.3)	99.9 (99.3)	100.0 (100.0)	99.3 (98.4)	99.8 (100.0)
Rmerge†	0.040 (0.384)	0.041 (0.256)	0.040 (0.239)	0.063 (0.272)	0.096 (0.148)
〈I〉/〈〈σ(I)〉	15.5 (1.3)	19.0 (2.7)	20.8 (2.9)	9.1 (2.1)	51.1 (23.3)
Space group	I222				P31
Unit-cell parameters (Å, °)	a = 79.1, b = 114.1, c = 114.7				a = b = 78.6, c = 71.9, α = β = 90, γ = 120
Refinement
Resolution range used for refinement (Å)				50.0–2.20	20.0–2.80
Rfactor‡ (%)				18.8	26.7
Rfree‡ (%)				22.9	29.9
No. of reflections used for refinement				24819	12171
Protein residues modelled				406 of 414	397 of 414
No. of protein atoms modelled				3061	3019
No. of water molecules modelled				158	16
Mean overall B value (Å2)				16.3	42.0
R.m.s.d. bond angle (°)				1.225	0.895
R.m.s.d. bond length (Å)				0.010	0.005
Ramachandran plot
Residues in most favoured regions (%)				85.5	82.4
Residues in additionally allowed regions (%)				14.5	17.3
Residues in generously allowed regions (%)				0.0	0.3
Residues in disallowed regions (%)				0.0	0.0

^† R _merge = .

^‡ R _factor = . R _free was calculated using 5% of the data that were excluded from refinement.