Molecular conformation of α-bungarotoxin as studied by nuclear magnetic resonance and circular dichroism

Abstract

We have examined the circular dichroism and nuclear magnetic resonance spectra of a long neurotoxin, α-bungarotoxin, over a wide range of pH values and temperatures, and under high salt conditions. The observations are interpreted partly in terms of the known crystal structure of this polypeptide. We support earlier findings of a greater degree of β-sheet structure in solution than has been reported by X-ray crystallography and, importantly, the invariant residue associated with neurotoxicity, Trp29, is shown to be in a similar environment to that found in α-cobratoxin and LS III from Laticauda semifasciata. The implications of this observation for structure/function relationships are outlined.