Open AccessRole of lysine and tryptophan residues in the biological activity of toxin VII (Ts γ) from the scorpion Tityus serrulatus
Author(s) -
Hassani Oussama,
Mansuelle Pascal,
Cestèle Sandrine,
Bourdeaux Madeleine,
Rochat Hervé,
Sampieri François
Publication year - 1999
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1327.1999.00152.x
Subject(s) - chemistry , venom , tryptophan , neurotoxin , edman degradation , biochemistry , toxin , circular dichroism , lysine , peptide , scorpion , stereochemistry , amino acid , peptide sequence , gene
Toxin VII (TsVII), also known as Ts γ, is the most potent neurotoxin in the venom of the Brazilian scorpion Tityus serrulatus. It has been purified to homogeneity using a new fast and efficient method. Chemical modification of TsVII with the tryptophan‐specific reagent o ‐nitrophenylsulfenyl chloride yielded three modified derivatives (residues Trp39, Trp50 and Trp54). Acetylation of TsVII mostly generated the monoacetylated Lys12 derivative. No side reactions were detected, as indicated by endoproteinase Lys‐C peptide mapping, Edman degradation and electrospray mass spectrometry. Circular dichroism and fluorimetric measurements showed that none of the chemical modifications altered the overall structure of the derivatives. The acetylation of Lys12 or the sulfenylation of Trp39 or Trp54 led to a loss of both toxicity in mice and apparent binding affinity for rat brain and cockroach synaptosomal preparations. Sulfenylation of Trp50, however, moderately affected the toxicity of TsVII in mice and had almost no effect on its binding properties. A 3‐dimensional model of TsVII was constructed by homology modeling. It suggests that the most reactive residues (Lys1 2 and Trp39 and Trp54) are all important in the functional disruption of neuronal sodium channels by TsVII, and are close to each other in the hydrophobic conserved region.