| Abstract
| - A new NMR method is proposed which enables the measurement of projection angles in the boundconformation of a weakly binding ligand complexed to its receptor. The method is based on the cross-correlatedrelaxation mechanism. In analogy to the transferred NOE experiment (trNOE), cross-correlated relaxation canbe transferred and measured at the resonances of the free ligand (trCCR), provided the koff rate is within thetime scale of the experiment. The concept is validated by the structure determination of an interleukin-4 (IL-4) receptor-derived partially 13C- and 15N-labeled phosphotyrosine peptide ligated to STAT-6. Distances havebeen obtained by trNOE experiments, and the torsion angle Pro(ψ) has been determined using trCCR, measuringeither cross-correlated HN−N/Hα−Cα dipole−dipole relaxation or cross-correlated Hα−Cα dipole/CO chemicalshift anisotropy relaxation. The resulting structure has been described.
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