Table 1.
Structural statistics for the solution structure of IL-33
| Number of structural restraints | 〈SA〉* | 〈SA〉water refined* |
|---|---|---|
| NOE-derived distance restraints | ||
| Total (unambiguous/ambiguous) | 4693 (4661/32) | |
| intraresidual | 1714 (1712/2) | |
| sequential | 909 (898/11) | |
| medium range | 423 (419/4) | |
| long range | 1647 (1632/15) | |
| Dihedral restraints | 245 | |
| φ | 123 | |
| ψ | 122 | |
| Hydrogen bonds † | 76 | |
| Violations | ||
| R.m.s.d from experimental restraints | ||
| NOE distance restraints (Å) | 0.0055 ± 0.0006 | 0.0115 ± 0.0018 |
| Dihedral restraints (°) | 0.15 ± 0.02 | 0.43 ± 0. 05 |
| NOE distance violations | ||
| Number > 0.1 Å | 1.9 ± 0.9 | 13.6 ± 3.2 |
| Number > 0.3 Å | 0 | 0.7 ± 1.0 |
| Dihedral violations | ||
| Number > 1° | 1.3 ± 0.9 | 13.7 ± 2.8 |
| Number > 2° | 0 | 3.2 ± 1.3 |
| R.m.s.d. from idealized geometry | ||
| Bonds (Å) | 0.00114 ± 0.00003 | 0.00353 ± 0.00009 |
| Angles (°) | 0.278 ± 0.002 | 0.486 ± 0.010 |
| Impr (°) | 0.149 ± 0.007 | 1.518 ± 0.096 |
| Coordinate precision ¶ | ||
| Backbone (all residues) | 1.30 ± 0.27 | 1.36 ± 0.23 |
| All heavy atoms (all residues) | 1.50 ± 0.20 | 1.54 ± 0.18 |
| Backbone (structured regions) | 0.36 ± 0.05 | 0.46 ± 0.06 |
| All heavy atoms (structured regions) | 0.74 ± 0.06 | 0.81 ± 0.06 |
| Stereochemistry # | ||
| Ramachandran plot (%) (all residues) | ||
| Percentage in most favored regions | 75.2 ± 3.0 | 77.2 ± 1.6 |
| Percentage in additionally allowed regions | 23.7 ± 3.2 | 21.5 ± 1.7 |
| Percentage in generously allowed regions | 0.8 ± 0.8 | 0.8 ± 0.7 |
| Percentage in disallowed regions | 0.3 ± 0.6 | 0.6 ± 0.3 |
| Ramachandran plot (%) (structured regions) | ||
| Percentage in most favored regions | 82.6 ± 2.5 | 83.8 ± 2.0 |
| Percentage in additionally allowed regions | 17.4 ± 2.5 | 16.1 ± 2.2 |
| Percentage in generously allowed regions | 0 | 0.2 ± 0.4 |
| Energies (kcal mol−1) ‡ | ||
| ENOE | 7.5 ± 1.7 | 32. 2 ± 10 |
| ECDIH | 0.4 ± 0.1 | 2.9 ± 0.7 |
| Ebond | 3.3 ± 0.2 | 31.5 ± 1.6 |
| Eangles | 54.1 ± 0.8 | 165.0 ± 7.0 |
| Eimpr | 4.4 ± 0.4 | 458.5 ± 60 |
〈SA〉 is an ensemble of the ten lowest energy solution structures of IL-33 (out of 100 calculated). The CNS Erepel function was used to simulate van der Waals interactions with an energy constant of 25.0 kcal mol−1Å−4 using ‘PROLSQ’ van der Waals radii. 1 kcal=4.18 kJ. For 〈SA〉 water refined, the ensemble of 〈SA〉 structures was refined in a shell of water.
Hydrogen bonds were derived from slowly exchanging amide protons and were applied as two distance restraints with bounds of 1.8–2.3 Å (H–O) and 2.8–3.3 Å (N–O).
Coordinate precision is given as the Cartesian coordinate r.m.s.d. of the ten lowest-energy structures in the NMR ensemble with respect to their mean structure for the full length IL-33 and the structured regions of IL-33 (residues 10–39, 47–56, 71–142 and 151–158).
Structural quality was analyzed using PROCHECK (Laskowski et al., 1996) for full length IL-33 and for the structured regions of IL-33 (residues 10–39, 47–56, 71–142 and 151–158).
NOESY derived distance restraints were used with a soft square-well potential using an energy constant of 50 kcal mol−1 Å−2. Dihedral angle restraints were applied using an energy constant of 200 kcal mol−1 rad−2. The force constants were 1000 kcal mol−1 Å−2 for bond length and 500 kcal mol−1 rad−2 for angles and improper dihedrals.