ESTIMATES OF PHI-TORSION AND PSI-TORSION ANGLES IN PROTEINS FROM ONE-BOND, 2-BOND AND 3-BOND NUCLEAR SPIN-SPIN COUPLINGS - APPLICATION TO STAPHYLOCOCCAL NUCLEASE

Calculated coupling constants ((3)J(HNH alpha), (1)J(C alpha H alpha), (2)J(C'H alpha), (1)J(C alpha N) and (2)J(C alpha N)) from our accompanying paper [Edison, A.S. et al. (1994) J. Biomol. NMR, 4, 519-542] have been used to generate error surfaces that can provide estimates of the phi and psi angles in proteins. We have used experimental coupling data [(3)J(HNH alpha): Kay, L.E. et al. (1989) J. Am. Chem. Sec., 111, 5488-5490; (1)J(C alpha H alpha): Vuister, G.W. et al. (1993) J. Biemol. NMR, 3, 67-80; (2)J(C'H alpha): Vuister, G.W. and Bar, A. (1992) J. Biomol. NMR, 2, 401405; (1)J(C alpha N) and (2)J(C alpha N): Delaglio, F. et al. (1991) J. Biomol. NMR, 1, 439-446] to create error surfaces for selected residues of the protein staphylococcal nuclease. The residues were chosen to include ah those with five experimental couplings, as well as some with four experimental couplings, to demonstrate the relative importance of (3)J(HNH alpha) and (1)J(C alpha H alpha). For most of the cases, we obtained good agreement between the X-ray structure [Loll, P.J. and Lattman, E.E. (1989) Protein Struct. Funct. Genet., 5, 183-201] and the NMR data.