Solution Structure of Discrepin, a New K+-Channel Blocking Peptide from the α-KTx15 Subfamily

• Published in: Biochemistry (Easton) Vol. 45; no. 6; pp. 1795 - 1804
• Main Authors: Prochnicka-Chalufour, Ada, Corzo, Gerardo, Satake, Honoo, Martin-Eauclaire, Marie-France, Murgia, Anna Rosa, Prestipino, Gianfranco, D'Suze, Gina, Possani, Lourival D, Delepierre, Muriel
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 14.02.2006
• Subjects: Animals; Binding Sites; Cells, Cultured; Cerebellum - cytology; Chromatography, High Pressure Liquid; Magnetic Resonance Spectroscopy; Models, Molecular; Neurotoxins - chemistry; Potassium Channel Blockers - chemistry; Potassium Channel Blockers - pharmacology; Protein Structure, Secondary; Rats; Rats, Wistar; Scorpion Venoms - chemistry; Scorpion Venoms - isolation & purification; Scorpion Venoms - pharmacology
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi0519248

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 α-KTx15 subfamily of scorpion toxins. Six members of the α-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 α/β scaffold, characteristic of scorpion toxins. Some features of the proposed interacting surface between the toxin and channel as well as the opposite “α-helix surface” are discussed in comparison with those of other α-KTx15 members. Both n- and s-discrepin exhibit similar physiological actions as verified by patch−clamp and binding and displacement experiments.