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

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Abstract
1H(i)-15N(i)-13C′(i) dipole-chemical shift anisotropy (CSA) relaxation interference was quantified for the 13C,15N labeled zinc-finger protein qCRP2(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 φand ψtaken from the solution structure. 1H(i)-15N(i)-13C′(i) as well as 13Cα(i)-1Hα(i)-13C′(i) dipole-CSA cross-correlation rates were subsequently used to improve 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 values obtained from crystal structures of other zinc-finger proteins and thus establish the utility of this approach to improve the metal-binding site geometry of zinc-finger proteins studied by NMR spectroscopy in solution.