The high-resolution NMR structure of the R21A Spc-SH3:P41 complex: Understanding the determinants of binding affinity by comparison with Abl-SH3

Table 3 Structural statistics for the 20 conformers of the R21A Spc-SH3:P41 complex¹

Distance restraints
Ambiguous Interaction Restraints	33
Intra-molecular NOE-derived Restraints:
SH3	1507
p41	17
Intermolecular NOE-derived Restraints	38
All	1595
Violations ²
violations > 0.3 Å	0
violations > 0.1 Å	0.2 +/- 0.4
RMSD from idealized covalent geometry
Bonds (Å)	0.0051 +/- 0.00026
Angles (°)	0.617 +/- 0.025
Impropers (°)	0.531 +/- 0.019
Dihedrals (°)	21.6 +/- 0.9
CNS Interaction energies (kcal/mol)
E_int	-92.98 +/- 3.06
E_vdw	- 47.02 +/- 2.09
E_elec	-45.96 +/- 3.95
Buried Surface Area (Å²)	940.6 +/- 15.3
Pairwise r.m.s.d. ³ in Å
Backbone N,CA,C' of residues 7–61 of SH3	0.24 +/- 0.05
Heavy atoms of residues 7–61 of SH3	0.63 +/- 0.17
Interface backbone N,CA,C'	0.460
Ramachandran plot ⁴
Most favored regions (%)	86.2
Additional allowed regions (%)	11.4
Generously allowed regions (%)	1.2
Disallowed regions (%)	1.3

¹The statistics is obtained from an ensemble of twenty water-refined solution structures for the R21A Spc-SH3:P41 complex.
²Violations reported only for the interaction, p41 intra-molecular and intermolecular NOE-derived restraints.
³Coordinate precision is given as the average pairwise Cartesian coordinate root mean square deviations over the ensemble. The interface is defined as residues 7–61 of R21A Spc-SH3 and residues 1–10 of p41. These sequence regions were also used for clustering.
⁴Values obtained from the PROCHECK analysis⁴⁶ for the SH3 domain excluding the first six highly flexible residues.

ISSN: 1472-6807