title: Solution structure of discrepin, a new K+-channel blocking peptide from the alpha-KTx15 subfamily.
abstract: Discrepin, isolated from the venom of the Venezuelan scorpion Tityus discrepans, blocks preferentially the I(A) currents of the voltage-dependent K+ channel of rat cerebellum granular cells in an irreversible way. It contains 38 amino acid residues with a pyroglutamic acid as the N-terminal residue [D'Suze, G., Batista, C. V., Frau, A., Murgia, A. R., Zamudio, F. Z., Sevcik, C., Possani, L. D., and Prestipino, G. (2004) Arch. Biochem. Biophys. 430, 256-63]. It is the most distinctive member of the alpha-KTx15 subfamily of scorpion toxins. Six members of the alpha-KTx15 subfamily have been reported so far to be specific for this subtype of the K+ channel; however, none of them have had their three-dimensional structure determined, and no information for the residues possibly involved in channel recognition and binding is available. Natural discrepin (n-discrepin) was prepared from scorpion venom, and its synthetic analogue (s-discrepin) was obtained by solid-phase synthesis. Analysis of two-dimensional 1H NMR spectra of n- and s-discrepin indicates that both peptides have the same structure. Here we report the solution structure of s-discrepin determined by NMR using 565 meaningful distance constraints derived from the volume integration of the two-dimensional NOESY spectrum, 22 dihedrals, and three hydrogen bonds. Discrepin displays the alpha/beta scaffold, characteristic of scorpion toxins. Some features of the proposed interacting surface between the toxin and channel as well as the opposite "alpha-helix surface" are discussed in comparison with those of other alpha-KTx15 members. Both n- and s-discrepin exhibit similar physiological actions as verified by patch-clamp and binding and displacement experiments.
authors.affiliation: Unité de RMN des Biomolécules URA 2185 CNRS, Institut Pasteur, 28 Rue du Dr Roux, 75724 Paris Cedex 15, France.
authors.forename: Ada
authors.initials: A
authors.lastname: Prochnicka-Chalufour
authors.forename: Gerardo
authors.initials: G
authors.lastname: Corzo
authors.forename: Honoo
authors.initials: H
authors.lastname: Satake
authors.forename: Marie-France
authors.initials: MF
authors.lastname: Martin-Eauclaire
authors.forename: Anna Rosa
authors.initials: AR
authors.lastname: Murgia
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Prestipino
authors.forename: Gina
authors.initials: G
authors.lastname: D'Suze
authors.forename: Lourival D
authors.initials: LD
authors.lastname: Possani
authors.forename: Muriel
authors.initials: M
authors.lastname: Delepierre
mesh_terms: D000818:Animals; D001665:Binding Sites; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology; D002851:Chromatography, High Pressure Liquid; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009498:Neurotoxins / Q000737:chemistry; D026902:Potassium Channel Blockers / Q000737:chemistry* / Q000494:pharmacology; D017433:Protein Structure, Secondary; D051381:Rats; D017208:Rats, Wistar; D012604:Scorpion Venoms / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology
chemical_list: D009498:Neurotoxins; D026902:Potassium Channel Blockers; D012604:Scorpion Venoms; C492486:discrepin peptide, rat; C509989:discrepin protein, Tityus discrepans