Proton NMR assignments and regular backbone structure of bovine pancreatic ribonuclease A in aqueous solution.

Proton NMR assignments have been made for 121 of the 124 residues of bovine pancreatic ribonuclease A (RNase A). During the first stage of assignment, COSY and relayed COSY data were used to identify 40 amino acid spin systems belonging to alanine, valine, threonine, isoleucine, and serine residues. Approximately 60 other NH-alpha CH-beta CH systems were also identified but not assigned to specific amino acid type. NOESY data then were used to connect sequentially neighboring spin systems; approximately 475 of the possible 700 resonances in RNase A were assigned in this way. Our assignments agree with those for 20 residues assigned previously [Hahn, U., & Rüterjans, H. (1985) Eur. J. Biochem. 152, 481-491]. Additional NOESY correlations were used to identify regular backbone structure elements in RNase A, which are very similar to those observed in X-ray crystallographic studies [Wlodawer, A., Borkakoti, N., Moss, D. S., & Howlin, B. (1986) Acta Crystallogr. B42, 379-387].