An efficient 3D NMR technique for correlating the proton and 15N backbone amide resonances with the alpha-carbon of the preceding residue in uniformly 15N/13C enriched proteins.

A 3D NMR technique is described which correlates the amide proton and nitrogen resonances of an amino acid residue with the C alpha chemical shift of its preceding residue. The technique uses a relay mechanism, transferring magnetization from 15N to 13C alpha via the intervening carbonyl nucleus. This method for obtaining sequential connectivity is less sensitive to large line widths than the alternative HNCA experiment. The technique is demonstrated for the protein calmodulin, complexed with a 26 amino acid fragment of skeletal muscle myosin light chain kinase.