NMR-STUDIES OF A COBALT-SUBSTITUTED ZINC FINGER PEPTIDE

Nuclear magnetic resonance studies of the complex between the consensus zinc finger peptide CP-1 and the paramagnetic ion Co(II) have allowed the orientation and anisotropy of the magnetic susceptibility tensor to be determined. Two approaches were used. First, 70 resonances were assigned for the CP-1-Co(II) complex using a combination of 2-D NMR techniques and characterization of sequence variants. The tensor was determined by maximizing the agreement between observed and calculated chemical shifts while varying the orientation and anisotropy of the tensor. The second approach compared the observed and calculated integrated spectra of the Co(II) complex while optimizing the tensor parameters. Both methods found the axial and equatorial anisotropies of the tensor to be chi(ax) = chi(zz) - 0.5(chi(xx) + chi(yy)) = 2280 +/- 400 VVk and chi(eq) = chi(xx) - chi(yy) = 280 +/- 310 VVk. The largest value of the magnetic susceptibility tensor lies approximately along the bisector of one of the sulfur-Co(II)-nitrogen angles. The knowledge of this tensor will allow refinement of the three-dimensional structure of the peptide and its complexes with DNA with constraints not available from traditional NMR studies.