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Bacillus thuringiensiscrystal protein: Effect of chemical modification of the cysteine and lysine residues

Authors
Journal
Journal of Invertebrate Pathology
0022-2011
Publisher
Elsevier
Publication Date
Volume
59
Issue
1
Identifiers
DOI: 10.1016/0022-2011(92)90114-j
Keywords
  • Bacillus Thuringiensis
  • Choristoneura Fuminifera
  • Chemical Modification
  • Protoxin
  • Solubility
  • Cysteine
  • Sulfhydryl
  • Lysine
  • Amino
Disciplines
  • Biology

Abstract

Abstract The 16 cysteine residues of reduced protoxin from Bacillus thuringiensis subsp. kurstaki HD-73 can be quantitatively reacted with: (a) iodoacetic acid, to give carboxymethyl protoxin; (b) iodoacetamide, giving carbaminomethyl protoxin and (c) N-(β-iodoethyl)trifluoroacetamide to give aminoethyl protoxin. The carboxymethyl derivative was found to be significantly more soluble at neutral pH values where both the native protoxin and the carbaminomethyl derivative exhibit low solubilities. At the alkaline pH values (pH 9.5–10.5) normally used to solubilize the crystal protein, the native protein was slightly more soluble than either the carboxymethyl or the carbaminomethyl derivatives. The aminoethyl derivative had an extremely low solubility at all pH values. Succinic anhydride reacted with only 35% of the lysine residues in both the carboxymethyl and the carbaminomethyl protoxin derivatives. Nonetheless, these succinylated protoxins exhibited significantly increased solubilities at neutral pH values. All the derivatives were found to retain full insecticidal activity toward spruce budworm ( Choristeneura fufimerana) larvae. It is concluded that all the cysteine residues and modified lysine residues are on the surface of the protein and that derivatization does not alter the conformation of the solubilized protoxin.

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