Table 1.

Data collection and refinement parameters

Diffraction data
Space group	R3
Cell constants	a = b = 99.6 Å, c = 97.0 Å
Limiting resolution	2.5 Å
No. of measured reflections	33,698
No. of unique reflections	12,532
Rmerge*	4.9%
Completeness (25.0–2.5 Å)	99.3%
(2.55–2.5 Å)	95.8%
I/s(I)	9.5
Refinement and final model
Resolution range	8.0–2.5 Å
Reflections used	12,015
Crystallographic R factor† (free R factor‡)	18.6% (25.9%)
R m.s. deviations  bond lengths	0.010 Å
bond angles	1.411°
No. of non-hydrogen protein atoms	3,070
Calcium ions	5
Solvent molecules	152

^*R_merge = σ[I(h)_i − 〈I(h)〉]/σ〈I(h)〉; I(h)_i is the observed intensity of the ith measurement of reflection h, and 〈I(h)〉 the mean intensity of reflection h calculated after loading and scaling. 

^†R factor = σ[|F_obs| − F_calc|]/σ|F_obs| × 100. 

^‡R_free was calculated randomly omitting 10% of the observed reflections from refinement and R factor calculation.