Table 1. Data-collection, phasing and refinement information.

Values in parentheses are for the highest resolution shell.

Unit-cell parameters (Å, °)	a = 50.36, b = 80.78, c = 104.77, β = 100.21
Space group	P21 (No. 4)
Data collection
Wavelength (Å)	0.97918
No. of images	242
Resolution (Å)	20–2.55 (2.59–2.55)
No. of unique reflections	26859 (1205)
Completeness (%)	98.6 (89.9)
Mean I/σ(I)	31.1 (3.3)
Redundancy	4.3 (2.5)
Rmerge†	0.088 (0.263)
Refinement
Resolution range (Å)	20–2.60
No. of reflections (work/test)	24041/1224
Rcryst/Rfree‡	0.217/0.287
R.m.s.d. (bond lengths) (Å)	0.0041
R.m.s.d. (bond angles) (Å)	1.09
Average B (chain A/chain B) (Å2)	45.7/52.9
No. of non-H protein atoms	6512
No. of Zn atoms	4
No. of water molecules	180

^† R _merge = , where I _i(hkl) is the intensity of the ith observation and 〈I(hkl)〉 is the mean for that set of observations.

^‡ R _cryst = , where |F _obs| and |F _calc| are the observed and calculated structure-factor amplitudes for reflection hkl in the working set; R _free is the same for the test set.