Table 2.

Refinement statistics

Measurement	Value
Resolution, Å	20–2.0
No. of unique reflections	65,700
No. of parameters to fit	12,660
σ cutoff	None
R factor, %	18.4
Rfree, %	20.0
rmsd bonds, Å	0.005
rmsd angles, °	1.2
rmsdNCS,* Å	0.12
Average B factor of protein	25.2
Average B factor of water	32.7
No. of water molecules	279
Residues in
Ramachandran plot, %
Most favored	90.6
Additional	8.7
Disallowed†	0.7

^*Three models were built. The rmsd is an average of the rmsd values between AB, BC, and AC. 

^† The only residue in a disallowed main chain conformation is Cys-100. This is consistent with its proposed role as the nucleophile (see text).