X-ray data collection and refinement statistics, Values in parentheses are for the last resolution shell.

aRsym is defined as ∑|(I-)|/∑I, where I is the intensity individual reflection and is the average intensity for this reflection; the summation is over all intensities.bRcryst = |Fo|−∥Fc|/Fo for all reflections.cRfree is the same as Rcryst, but calculated on the 5% of data excluded from refinement.dNo σ cut-offs used on the refinement (F>0σF).eEngh RA, Huber R (1991) Acta Cryst A47: 392–400. Engh RA, Huber R (2001) International Tables for Crystallography, Vol. F, edited by M. G. Rossmann & E. Arnold, pp. 382–392. Dordrecht: Kluwer Academic Publishers.fKleywegt GJ, Jones TA (1996). Structure 15: 1395–1400.