Sequential 1H-NMR assignment and solution structure of bovine pancreatic ribonuclease A

Assignments for 1H-NMR resonances of most of the residues of bovine pancreatic ribonuclease (RNase A) have been obtained by sequence-specific methods. Identification and classification of spin systems have been carried out by two-dimensional phase-sensitive correlated spectroscopy (360 MHz) and single relayed coherence transfer spectroscopy. Sequence-specific assignments have been achieved by phase-sensitive two-dimensional nuclear Overhauser effect spectroscopy. To overcome the problem of spectral overlap use has been made of (a) an exhaustive analysis of partly exchanged RNase A (spectra in D2O), (b) a comparison with the subtilisin-modified enzyme (RNase S) and (c) small spectral perturbations caused by changes in pH and temperature. The secondary structure elements have been identified from the observed sequential, medium and long-range nuclear Overhauser effects together with data from amide-exchange rates. All information collected leads to the conclusion that the crystal and the solution structures are closely similar.