Intraresidue H-1-N-15-C-13 ' and H-1 alpha-C-13 alpha-C-13 ' dipole-CSA relaxation interference as a source of constraints for structural refinement of metal-binding sites in zinc-finger proteins

H-1(i)-N-15(i)-C-13'(i) dipole-chemical shift anisotropy (CSA) relaxation i nterference was quantified for the C-13,N-15 labeled zinc-finger protein qC RP2(LIM2). The cross-correlation rates obtained for residues located in the metal coordination sites of qCRP2(LIM2) show a high degree of correlation with the peptide plane torsion angles phi and psi taken from the solution s tructure. H-1(i)-N-15(i)-C-13'(i) as well as C-13 alpha (i)-H-1 alpha (i)-C -13'(i) dipole-CSA cross-correlation rates were subsequently used to improv e the geometry of the metal binding site. The optimized dihedral angles of the two zinc-binding sites in qCRP2(LIM2) are in better agreement with valu es obtained from crystal structures of other zinc-finger proteins and thus establish the utility of this approach to improve the metal-binding site ge ometry of zinc-finger proteins studied by NMR spectroscopy in solution.