Open AccessChemical synthesis and characterization of Pi1, a scorpion toxin from Pandinus imperator active on K + channels
Author(s) -
Fajloun Ziad,
Carlier Edmond,
Lecomte Catherine,
Geib Sandrine,
di Luccio Eric,
Bichet Delphine,
Mabrouk Kamel,
Rochat Hervé,
De Waard Michel,
Sabatier JeanMarc
Publication year - 2000
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.1432-1327.2000.01577.x
Subject(s) - scorpion toxin , toxin , xenopus , biochemistry , chemistry , peptide , in vivo , biophysics , venom , biology , stereochemistry , scorpion , gene , microbiology and biotechnology
Pi1 is a 35‐residue toxin cross‐linked by four disulfide bridges that has been isolated from the venom of the chactidae scorpion Pandinus imperator . Due to its very low abundance in the venom, we have chemically synthesized this toxin in order to study its biological activity. Enzyme‐based proteolytic cleavage of the synthetic Pi1 (sPi1) demonstrates half‐cystine pairings between Cys4–Cys25, Cys10–Cys30, Cys14–Cys32 and Cys20–Cys35, which is in agreement with the disulfide bridge organization initially reported on the natural toxin. In vivo , intracerebroventricular injection of sPi1 in mice produces lethal effects with an LD 50 of 0.2 µg per mouse. In vitro , the application of sPi1 induces drastic inhibition of Shaker B (IC 50 of 23 n m ) and rat Kv1.2 channels (IC 50 of 0.44 n m ) heterologously expressed in Xenopus laevis oocytes. No effect was observed on rat Kv1.1 and Kv1.3 currents upon synthetic peptide application. Also, sPi1 is able to compete with 125 I‐labeled apamin for binding onto rat brain synaptosomes with an IC 50 of 55 p m . Overall, these results demonstrate that sPi1 displays a large spectrum of activities by blocking both SK‐ and Kv1‐types of K + channels; a selectivity reminiscent of that of maurotoxin, another structurally related four disulfide‐bridged scorpion toxin that exhibits a different half‐cystine pairing pattern.