Table 1. Diffraction data and refinement statistics.

Values in parentheses are for the highest resolution shell.

	Native form	Iron-soaked form
Crystal parameters
Space group	P212121	P212121
Unit-cell parameters ()	a = 94.7, b = 98.4, c = 208.9	a = 94.5, b = 98.0, c = 208.4
Solvent content (%)	43.7	43.2
Matthews coefficient (3Da1)	2.18	2.16
No. of molecules in asymmetric unit	12	12
Data collection
X-ray wavelength ()	1.0000	1.0000	1.7400	1.7500
Resolution ()	50.01.25 (1.271.25)	50.01.30 (1.321.30)	30.02.00 (2.032.00)	30.02.00 (2.032.00)
I/(I)	18.6 (3.43)	17.8 (2.40)	18.9 (5.60)	20.0 (6.24)
No. of observed reflections	2854420	1768328	424197	422495
No. of unique reflections	531051	428932	117185	116841
Completeness (%)	99.7 (99.9)	90.9 (89.6)	88.7 (83.4)	88.6 (83.2)
Multiplicity	5.4 (4.7)	4.1 (2.8)	3.6 (3.6)	3.6 (3.7)
R merge †	0.075 (0.557)	0.061 (0.396)	0.054 (0.204)	0.042 (0.176)
Refinement
No. of used reflections	504240	407378
R work ‡/R free §	0.164/0.205	0.153/0.173
Mean temperature factor (2)	18.4	25.2
Model composition
No. of amino acids	1839	1835
No. of non-H atoms	16660	16201
No. of iron ions	0	12
No. of magnesium ions	6	4
No. of sulfate ions	6	6
No. of water molecules	1644	1327
Geometry
R.m.s.d. bond lengths ()	0.022	0.022
R.m.s.d. bond angles ()	1.95	1.95
Ramachandran plot, residues in
Favoured region (%)	99.1	99.3
Allowed region (%)	0.9	0.7
Outlier region (%)	0.0	0.0

^† R _merge = , where I_i(hkl) is the intensity measured for a given reflection and I(hkl) is the average intensity for multiple measurements of this reflection.

^‡ R _work = , where F _obs and F _calc are the observed and calculated structure-factor amplitudes, respectively, for 95% of the reflection data used in the refinement.

^§ R _free = for 5% of the reflection data that were excluded during refinement.