Résumé
The solution structure of toxin gamma (60 residues, 4 disulfides) from Naja nigricolis was determined by proton nmr and molecular modeling with DIANA and X-PLOR. The structures were calculated using 489 distance and 81 dihedral angle constraints. The average atomic rms deviation between the nine refined structures and the average structure is 0.118 nm for the backbone atoms. Toxin gamma has on overall folding consisting of three loops stabilized by the four disulfides and forming a two-and a three-stranded B-sheet (loop I and loops II, III, respectively). The same type of folding has been observed for two homologous cardiotoxins.