Table 1

Data collection, phasing, and refinement statistics

Native*BR1BR2
Resolution, Å20–1.320–2.420–1.8
Reflections17,4654,8336,283
% complete (last shell)95.0% (91.8%)83.4% (43.6%)91.6% (68.2%)
Rmerge (last shell)6.0% (26.7%)2.5% (2.7%)3.5% (5.7%)
Anomalous dataNoYesNo
Phasing statistics
 Number of bromine sites12
 Resolution, Å20–2.420–2.0
 Phasing power2.381.72
 RCullis (iso)0.580.64
 RCullis (ano)0.78
 Combined figure of merit (20 Å–2.0 Å) 0.52
Refinement statistics
 R-factor (15,734 reflections)12.6%
 Free R-factor (1,731 reflections)17.7%
 Number of atoms749
 Number of water molecules178
 Number of calcium ions4
 rmsd bond lengths0.009 Å
 rmsd bond angle lengths0.025 Å
  • Rmerge is defined as Σ|I − 〈I〉|/ΣI. Phasing power is defined as rms FH/rms closure error. RCullis (iso) = ratio of lack of closure to isomorphous difference. RCullis (ano) = ratio of lack of closure to anomalous difference. Figure of merit is defined as cos〈σ(Δφ)〉. R-factor = Σ∥Fo| − |Fc∥/Σ|Fo|, where |Fo| and |Fc| are the observed and calculated structure factors, respectively. Free R-factor is same as R-factor but calculated with 10% of the reflections excluded from refinement. 

  • * Native data set was obtained by merging data from two crytals as described in Materials and Methods

  • Number reflects Bijvoet pairs treated separately.