Solution structure of Pi4, a short four-disulfide-bridged scorpion toxin specific of potassium channels.

J. Iñaki Guijarro (1) , Sarrah M'Barek (2) , Froylan Gómez-Lagunas (3) , Damien Garnier (1) , Hervé Rochat (2) , Jean-Marc Sabatier (2) , Lourival D. Possani (4) , Muriel Delepierre (1) , Lourrival Possani (4)

1 Résonance Magnétique Nucléaire des Biomolécules
2 Biochimie - Ingénierie des protéines
3 Department of Physiology, School of Medicine
4 Department of Molecular Medicine and Bioprocesses, Institut of Biotechnology

Pi4 is a short toxin found at very low abundance in the venom of Pandinus imperator scorpions. It is a potent blocker of K(+) channels. Like the other members of the alpha-KTX6 subfamily to which it belongs, it is cross-linked by four disulfide bonds. The synthetic analog (sPi4) and the natural toxin (nPi4) have been obtained by solid-phase synthesis or from scorpion venom, respectively. Analysis of two-dimensional (1)H NMR spectra of nPi4 and sPi4 indicates that both peptides have the same structure. Moreover, electrophysiological recordings of the blocking of Shaker B K(+) channels by sPi4 (K(D) = 8.5 nM) indicate that sPi4 has the same blocking activity of nPi4 (K(D) = 8.0 nM), previously described. The disulfide bonds have been independently determined by NMR and structure calculations, and by Edman-degradation/mass-spectrometry identification of peptides obtained by proteolysis of nPi4. Both approaches indicate that the pairing of the half-cystines is (6)C-(27)C, (12)C-(32)C, (16)C-(34)C, and (22)C-(37)C. The structure of the toxin has been determined by using 705 constraints derived from NMR data on sPi4. The structure, which is well defined, shows the characteristic alpha/beta scaffold of scorpion toxins. It is compared to the structure of the other alpha-KTX6 subfamily members and, in particular, to the structure of maurotoxin, which shows a different pattern of disulfide bridges despite its high degree of sequence identity (76%) with Pi4. The structure of Pi4 and the high amounts of synthetic peptide available, will enable the detailed analysis of the interaction of Pi4 with K(+) channels.

Domaines: Biologie structurale [q-bio.BM]

J. Iñaki Guijarro, Sarrah M'Barek, Froylan Gómez-Lagunas, Damien Garnier, Hervé Rochat, et al.. Solution structure of Pi4, a short four-disulfide-bridged scorpion toxin specific of potassium channels.. Protein Science, 2003, 12 (9), pp.1844-54. ⟨10.1110/ps.03186703⟩. ⟨pasteur-00364861⟩