Table I. Structural statistics of 20 final structures of the dimeric lac HP62–O1 operator complex^a.

R.m.s.d. (Å) with respect to meanb (backbone/heavy)
lac HP62 (left subunit)	0.34 ± 0.09/0.85 ± 0.24
lac HP62 (right subunit)	0.38 ± 0.10/0.86 ± 0.26
lac HP62 (dimer)	0.48 ± 0.13/0.93 ± 0.29
O1 operator	0.67 ± 0.37/0.62 ± 0.30
lac HP62–O1 operator	0.62 ± 0.29/0.82 ± 0.34
No. of experimental restraints
Protein (dimer)
Intraresidue NOEs	514
Sequential NOEs (|i – j| = 1)	419
Medium range NOEs (1<|i – j|<4)	260
Long-range NOEs (|i – j|>4)	246
Interprotein	28
Total NOEs	1467
Dihedral angle restraints	162
DNA NOEs	680
Protein–DNA NOEs	245
Protein–DNA hydrogen bonds	9
Restraint violationsc
NOE distances with violations >0.3 Å	2.9 ± 1.8
Dihedrals with violations >5°	4.2 ± 1.9
R.m.s.d. for experimental restraints
All distance restraints (2401) (Å)	0.06 ± 0.01
Torsion angles (162) (°)	4 ± 2
CNS energies from SAd
Evdw (kcal/mol)	–1096 ± 10
Eelec (kcal/mol)	–3077 ± 62
R.m.s.d. (Å) from idealized covalent geometry
Bonds (°)	0.003 ± 0.00
Angles (°)	0.54 ± 0.01
Impropers (°)	0.51 ± 0.01
Ramachandran analysis
Residues in the favoured region (%)	85.1
Residues in additional allowed regions (%)	13.8
Residues in generously allowed regions (%)	0.6
Residues in disallowed regions (%)	0.6

^aBased on 20 structures, obtained by simulated annealing in CNS followed by refinement in explicit water using NOE distance restraints, dihedral angle restraints, bonds, angles, impropers, dihedral angle, van der Waals and electrostatic energy terms (see Materials and methods).

^bResidues 3–59 for the protein and bp 2–21 for the operator are taken into account.

^cNo distances were violated by >0.5 Å.

^dThe non-bonded energies were calculated with the OPLS parameters using a 11.5 Å cut-off.