Effect of N-bromosuccinimide-modification of tyrosine side chains of cardiotoxin II of the Indian cobra on biological activity.
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Date
1987-03
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Abstract
The essential role of tyrosine residue(s) of cardiotoxin II in the biological activity
of the toxin was evaluated using N-bromosuccinimide. N-bromosuccinimide effected oxidation
of the tyrosine residues in cardiotoxin II with enhancement in absorbance at 260 nm.
The influence of various solvent media such as acetate-formate buffer (pH 4·0),0·01 Ν
H2SO4 (pH 2·0) and Tris-HCl buffer (pH 8·5) on oxidation of tyrosine residues was exa
mined. In comparison with 0·01 Ν H2S O4, acetate-formate buffer could prevent secondary
oxidations as revealed by lower consumption of oxidant, N-bromosuccinimide, to achieve
oxidation. In Tris-HCl buffer oxidation of tyrosine did not take place effectively. N-iodosuccinimide
caused only limited oxidation as evident from minor increase in absorbance at
260 nm. N-chlorosuccinimide was completely ineffective. Oxidation of cardiotoxin II with
3·75 equivalents of N-bromosuccinimide tyrosine residue led to complete loss of lethal activity.
However, the derivative retained the ability to protect bacterial protoplasts from
lysis in solutions of low tonicity. Unlike cardiotoxin II oxidized with N-chlorosuccinimide
(50 equivalents/mol of toxin) which retained lethal activity as well as the ability to protect
protoplasts from lysis, performic acid-oxidized toxin had lost both the activities.
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Keywords
Cardiotoxin II, Naja naja, N-bromosuccinimide oxidation, essential tyrosine, protoplast stabilization
Citation
Shashidharan P, Ramachandran L K. Effect of N-bromosuccinimide-modification of tyrosine side chains of cardiotoxin II of the Indian cobra on biological activity. Journal of Biosciences. 1987 Mar; 11(1-4): 287-297.