NMR strategy for determining Xaa-Pro peptide bond configurations in proteins: Mutants of staphylococcal nuclease with altered configuration at proline-117

A general approach has been developed for configurational analysis (cis or (trans) of Xaa-Pro peptide bonds in proteins. This approach, which entails selective 13 C labeling of Xaa and Pro residues in the protein and isotope-edited NMR, has been applied to mutants of staphylococcal nuclease with suspected altered configurations of the Lys 116 -Pro 117 peptide bond. The technique for monitoring proline configurations is based on differences in interproton distances between the H α of residue Xaa and the proline H δ or H α protons. Short (<2.5 A) XAA H α -Pro H δ interproton distances are diagnostic for the (trans configuration, whereas short (<2.5 A) XAA H α -Pro H δ interproton distances are diagnostic for the cis configuration