Estimates of ϕ and ψ torsion angles in proteins from one-, two- and three-bond nuclear spin-spin couplings: Application to staphylococcal nuclease

Summary

Calculated coupling constants (³J_H ^N _H ^α, ¹J_C ^α _H ^α, ²J_C′H ^α, ¹J_C ^α _N and ²J_C ^α _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 ϕ and ψ angles in proteins. We have used experimental coupling data [³J_H ^N _H ^α: Kay, L.E. et al. (1989) J. Am. Chem. Soc., 111, 5488–5490; ¹J_C ^α _H ^α: Vuister, G.W. et al. (1993) J. Biomol. NMR, 3, 67–80; ²J_C′H ^α: Vuister, G.W. and Bax, A. (1992) J. Biomol. NMR, 2, 401–405; ¹J_C ^α _N and ²J_C ^α _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 all those with five experimental couplings, as well as some with four experimental couplings, to demonstrate the relative importance of ³J_H ^N _H ^α and ¹J_C ^α _H ^α. 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.