Optical activity and conformation of cobra neurotoxin

Cobra neurotoxin from Formosan cobra (Naja naja atra) venom is a compact globular protein having an intrinsic viscosity of 4.5 mL/g. The protein is stable in 7.5 M urea but can be denatured in 4.1 M guanidine hydrochloride or at elevated temperature (above 70 degrees C). Its conformation remains vir...

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Bibliographic Details
Published in:Biochemistry (Easton) 1977-05, Vol.16 (9), p.1826-1830
Main Authors: Chen, Yee-Hsiung, Lo, Tung-Bin, Yang, Jen Tsi
Format: Article
Language:English
Subjects:
1-Propanol
Circular Dichroism
Ethylene Glycols
Guanidines
Hot Temperature
Optical Rotation
Protein Conformation
Snake Venoms - analysis
Urea
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Summary:Cobra neurotoxin from Formosan cobra (Naja naja atra) venom is a compact globular protein having an intrinsic viscosity of 4.5 mL/g. The protein is stable in 7.5 M urea but can be denatured in 4.1 M guanidine hydrochloride or at elevated temperature (above 70 degrees C). Its conformation remains virtually the same in solvents of lower polarity than water such as 1,2-ethanediol or a mixed solvent of 1-propanol-1,2-ethanediol-water (5:1:1 by volume). The circular dichroism spectrum is "atypical" in water in that the peptide chromophores show a small negative circular dichroic (CD) band at 215 nm, a large positive one at 199 nm, and another large negative one below 190 nm. The CD pattern resembles to some extent that of a beta form but differs in both positions and magnitudes from the latter. It agrees qualitatively with the theoretical calculations of the reverse beta bends, suggesting that cobra toxin contains a considerable amount of beta turns and possibly a mixture of beta form and beta turns.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi00628a010