Circular dichroism study of the unfolding-refolding of a cardiotoxin from Taiwan cobra (Naja naja atra) venom

• Published in: Biochemistry (Easton) Vol. 24; no. 20; pp. 5678 - 5685
• Main Authors: Galat, Andrzej, Yang, Chenchung, Blout, Elkan R
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.09.1985
• Subjects: Amino Acid Sequence; Biological and medical sciences; Circular Dichroism; Cobra Cardiotoxin Proteins - metabolism; Conformational dynamics in molecular biology; Disulfides - analysis; Elapid Venoms - metabolism; Fundamental and applied biological sciences. Psychology; Models, Molecular; Molecular biophysics; Protein Conformation; Proteins; Toxin; Vertebrata; Refolding; Venom; Unfolding; Reptilia; Circular dichroism; Ophidia; Conformational transition
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00341a059

Circular dichroism spectroscopy has been used to study the unfolding-refolding process of a cardiotoxin from Taiwan cobra (Naja naja atra) venom upon addition of fluoroalcohols or sodium dodecyl sulfate (SDS) to its aqueous solution. In these experiments, the disulfide bridges remained intact. The unfolding process has been found to be reversible both for fluoroalcohols and for SDS unfolding. The reversibility of the unfolding-refolding process of cardiotoxin in aqueous mixtures of fluoroalcohols was dependent on the volume per volume ratio of alcohol to water. SDS did not unfold the secondary structures of cardiotoxin whereas its tertiary structure was affected. If the SDS concentration in aqueous solution exceeded the critical micelle concentration value of SDS, a quasi-refolded state of cardiotoxin was observed. The mechanism of unfolding-refolding is discussed in terms of molecular interactions which might govern the protein conformation in solution.