Long-range 15N-1H correlation as an aid to sequential proton resonance assignment of proteins. Application to the DNA-binding protein ner from phage Mu.

A method is described for sequential resonance assignment of protein 1H-NMR spectra relying on the detection of long-range correlations between 15N and C alpha H atoms using 1H-detected heteronuclear multiple-bond correlation spectroscopy. In particular, the observation of the two-bond 15N(i)-C alpha H(i) and three-bond 15N(i)-C alpha H(i-1) correlations enables one to connect one residue with the next. Because the magnitude of the long-range couplings is small (less than 6 Hz), the sensitivity of this experiment is necessarily low and requires the use of 15N-enriched protein samples. Further, because the size of the 15N(i)-C alpha H(i-1) coupling is very sensitive to the psi backbone torsion angle, structural information can be derived. The application of this experiment is illustrated with the 75-residue DNA-binding protein ner from phage Mu.