Table 1.
| Experimental restraints | |
| long range NOEs (i - j > 10)1 | 459 |
| short range interresidue NOEs (i - j < 10) | 566 |
| restrictive intraresidue NOEs | 210 |
| paramagnetic restraints2 | 27 |
| 13C chemical shift restraints | 271 |
| Residual dipolar couplings (C12E5, Da=20 Hz, R = 0.283) | 102 |
| Residual dipolar couplings (fd, Da=13.1 Hz, R = 0.309) | 32 |
| J-coupling restraints (periodic) | 64 |
| dihedral angle restraints3 | 333 |
| total number of experimental restraints | 2,054 |
| Modeling restraints | |
| hydrogen bonds in regular secondary structure4 | 59 |
| harmonic and modeling restraints5 | 71 |
| total number of modeling restraints | 125 |
| Structural statistics over 17 models | |
| no. of distance violations > 0.5 Å | none |
| Goodness of fit of RDC restraints to structures | |
| C12E5 | R=1.00, Q=0.05 |
| fd | R=0.99, Q=0.12 |
| Ramachandran analysis7 | |
| residues in most favored regions | 80.9% |
| residues in additional allowed regions | 16.8% |
| residues in generously allowed regions | 2.3% |
| residues in dissallowed regions | 0.0% |
| Atypical χ1 rotamers8 | 1.2% |
| Side-chain steric interactions < 0.8 Å9 | <1% |
| backbone RMSD (Å) for 17 models | 0.62 |
i and j refer to residue numbers.
Paramagnetically broadened resonances were constrained to be ≤ 10 Å from the nickel.
Dihedral angle restraints were obtained by chemical shift analysis using TALOS (2004 edition) (Cornilescu et al., 1999) (see text).
Hydrogen bonds within regular secondary structure were determined by repeated occurrence in unrestrained structures.
Harmonic restraints and three hydrogen bonds were applied to model the paramagnetic region as described in text.
Ramachandran statistics were calculated using PROCHECK_NMR (Laskowski et al., 1996) and excludes prolines, glycines and terminal residues.
Sidechain dihedral angles (χ1) noted as low frequency by WHAT_CHECK (Hooft et al., 1996). No “bad” scores (lower than 0.30) were found in any structure. In eight of the 17 structures, residue 38 was identified as a rare conformer. In seven of the structures, residue 37 was identified as a rare conformer. Residues 7, 77 and 133 occur as rare conformers in more than one structure.
Steric interactions occurred in ten structures between the side chain atoms Cɛ2 of Trp 16 and Hɛ22 of Gln 27, and between Cζ2 of Trp 16 and Hɛ22 of Gln 27 in seven structures. Interactions between Hɛ21 of Gln 58 and Cγ1 Ile 61 occur in nine structures. Steric interactions were detected using the van der Waals subroutine of MOLMOL (Koradi et al., 1996).