Refolding of reduced short neurotoxins: circular dichroism analysis.
The four disulfide bonds of nine homologous short curare-like polypeptides are cleaved by reduced dithiothreitol. Air oxidation renaturations of the reduced compounds are followed by far-ultraviolet circular dichroism analysis, and the kinetics of refolding thus determined are compared. They indicate that three toxins refold 4--10 times more slowly than the six others. It is shown that a significant difference between the refolding kinetics still subsists when renaturations are made in the presence of various concentrations of thiol-disulfide exchange reagents or at various pH values. From an examination of the toxin sequences, it is proposed that a single additional amino acid insertion is responsible for the difference in the observed kinetics. This proposal is supported by temperature studies of renaturation kinetics.
D000818:Animals; D002942:Circular Dichroism; D004546:Elapid Venoms; D007700:Kinetics; D009498:Neurotoxins; D010084:Oxidation-Reduction; D011487:Protein Conformation; D011489:Protein Denaturation; D012910:Snake Venoms; D013045:Species Specificity; D013816:Thermodynamics; D014961:X-Ray Diffraction
D004546:Elapid Venoms; D009498:Neurotoxins; D012910:Snake Venoms