Molecular conformation of α-cobratoxin 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-cobratoxin over a wide range of pH values and temperatures, and in certain solvents and salts. The observations are interpreted in large part in terms of the known crystal structure of the peptide. While we find general agreement between the solution structure in physiological conditions and the crystal structure, there are important differences. The conformational position of His is quite different and this change affects several other residues to some degree. Again, the temperature dependence of Trp25 indicates that there is a lack of rigidity in another and different part of the molecule. The implications of our findings for structure/function relationships are outlined.