Table 1.
Data Collection and Refinement Statisticsa
| Data Collection and Phasing | Sulfur SAD, Form-I (in House) | Native, Form-I (Synchrotron) | Native, Form-II (Synchrotron) | Native, Form-II (in House) |
|---|---|---|---|---|
| Resolution | 100–1.90 (1.97–1.90) | 100–1.65 (1.71–1.65) | 100–1.90 (1.97–1.90) | 100–3.00 (3.11–3.00) |
| Reflections (total/unique) | 808,412/12,883 | 147,079/19,469 | 191,032/31,109 | 60,556/8,241 |
| Completeness | 99.9 (100.0) | 99.9 (99.8) | 99.4 (100.0) | 99.9 (99.9) |
| Rmeasb | 8.2 (50.7) | 8.0 (50.2) | 6.8 (56.8) | 10.3 (39.5) |
| Rmrgd-Fb | 2.8 (12.5) | 7.9 (40.9) | 7.2 (43.2) | 8.9 (27.5) |
| I/σ | 62.9 (56.0) | 13.9 (2.6) | 11.3 (2.2) | 19.0 (5.4) |
| FOM/Δϕ(°)–Mlpharec | 0.2/66 | |||
| FOM/Δϕ (°)–DMc | 0.7/51 | |||
| Refinement | Form-I (synchrotron) | Form-II (synchrotron) | ||
| Resolution (Å) | 100–1.65 (1.69–1.65) | 100–1.90 (1.95–1.90) | ||
| Number of reflections | 19,430 | 31,030 | ||
| Number of amino acids | 103 | 315 | ||
| Number of solvent atoms | 105 | 165 | ||
| Number of Ni2+ ions | – | 8 | ||
| Number of SO4−2 ions | 2 | – | ||
| Total number of atoms | 968 | 2,668 | ||
| Average B (all atoms) (Å2) | 28 | 45 | ||
| Rcryst (%)d | 15.7 (21.6) | 18.3 (24.5) | ||
| Rfree (%)d | 18.3 (26.3) | 22.6 (31.3) | ||
| RMSD bonds (Å) | 0.012 | 0.008 | ||
| RMSD angles (degrees) | 1.435 | 1.097 | ||
| φ,ψ Core region (%)e | 100 | 98 |
a
Numbers in parentheses correspond to values in the highest resolution shell.
b
Rmeas is the multiplicity weighted merging R-factor, and Rmrgd-F is an indicator of the quality of reduced data (Diederichs and Karplus, 1997).
c
Figure of merit (FOM): average absolute phase difference between final refined phases and experimental phases both before (MIphare) and after density modification (DM).
d
Rcryst, ∑|Fobs − Fcalc|/∑|Fobs|; Rfree, Rcryst calculated using 10% of the data that were excluded from the refinement.
e
Ramachandran plot quality as defined by Kleywegt and Jones (1996). In chain B of the form-II structure, Asn77 (φ,ψ = −111°, 73°) and Asn127 (φ,ψ = −135°, −159°) lie in the noncore region.