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Solution structure of Pi4, a short four‐disulfide‐bridged scorpion toxin specific of potassium channels
Author(s) -
Guijarro J. Iñaki,
M'Barek Sarrah,
GómezLagunas Froylan,
Garnier Damien,
Rochat Hervé,
Sabatier JeanMarc,
Possani Lourrival D.,
Delepierre Muriel
Publication year - 2003
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.03186703
Subject(s) - scorpion toxin , edman degradation , stereochemistry , chemistry , venom , crystallography , scorpion , peptide sequence , biochemistry , gene
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 α‐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 α/β scaffold of scorpion toxins. It is compared to the structure of the other α‐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.