X-ray data collection and structure refinement statistics.

MR indicates phasing by molecular replacement. Se-SAD indicates phasing performed using single wavelength anomalous dispersion of selenium. AU stands for asymmetric unit.
r.m.s.d is the root-mean square deviation from ideal geometry.
Rsym = ΣhklΣi |Ihkl,i−<Ihkl,i>|/ΣhklΣi |Ihkl,i| where <Ihkl,i> is the average intensity of the multiple hkl, i observations for symmetry-related reflections.
Rcryst = Σ|Fobs−Fcalc|/Σ|Fobs|. Fobs and Fcalc are observed and calculated structure factors, Rfree is calculated from a set of randomly chosen 5 to 10% of reflections, and Rcryst is calculated over the remaining 90 to 95% of reflections.
The refined occupancies of 100% (catalytic GDP) and 69% (external GDP) and atomic displacement factors of the two GDPs are indicated.