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Toxicon. 2017 Jul;133:136-144. doi: 10.1016/j.toxicon.2017.05.011. Epub 2017 May 11.

Pi5 and Pi6, two undescribed peptides from the venom of the scorpion Pandinus imperator and their effects on K+-channels.

Author information

1
Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autonoma de Mexico, Avenida Universidad, 2001, Cuernavaca, Morelos, 62210, Mexico.
2
Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autonoma de Mexico, Ciudad de Mexico, 04510, Mexico.
3
Department of Biophysics and Cell Biology, Faculty of Medicine, Research Center for Molecular Medicine, University of Debrecen, 1 Egyetem ter, Debrecen, 4032, Hungary.
4
Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autonoma de Mexico, Avenida Universidad, 2001, Cuernavaca, Morelos, 62210, Mexico. Electronic address: possani@ibt.unam.mx.

Abstract

This work reports the isolation, chemical and functional characterization of two previously unknown peptides purified from the venom of the scorpion Pandinus imperator, denominated Pi5 and Pi6. Pi5 is a classical K+-channel blocking peptide containing 33 amino acid residues with 4 disulfide bonds. It is the first member of a new subfamily, here defined by the systematic number α-KTx 24.1. Pi6 is a peptide of unknown real function, containing only two disulfide bonds and 28 amino acid residues, but showing sequence similarities to the κ-family of K-channel toxins. The systematic number assigned is κ-KTx2.9. The function of both peptides was assayed on Drosophila Shab and Shaker K+-channels, as well as four different subtypes of voltage-dependent K+-channels: hKv1.1, hKv1.2, hKv1.3 and hKv1.4. The electrophysiological assays showed that Pi5 inhibited Shaker B, hKv1.1, hKv1.2 and hKv1.3 channels with Kd = 540 nM, Kd = 92 nM and Kd = 77 nM, respectively, other studied channels were not affected. Of the channels tested only hKv1.2 and hKv1.3 were inhibited at 100 nM concentration of Pi6, the remaining current fractions were 68% and 77%, respectively. Thus, Pi5 and Pi6 are high nanomolar affinity non-selective blockers of hKv1.2 and hKv1.3 channels.

KEYWORDS:

Amino acid sequence; Ion-channel; K(+)-channel blocker; Pandinus imperator; Scorpion toxin

PMID:
28502745
DOI:
10.1016/j.toxicon.2017.05.011
[Indexed for MEDLINE]

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