Abstract
This communication reports the structural and functional characterization of urotoxin, the first K+ channel toxin isolated from the venom of the Australian scorpion Urodacus yaschenkoi. It is a basic peptide consisting of 37 amino acids with an amidated C-terminal residue. Urotoxin contains eight cysteines forming four disulfide bridges with sequence similarities resembling the α-potassium channel toxin 6 (α-KTx-6) subfamily of peptides; it was assigned the systematic number of α-KTx-6.21. Urotoxin is a potent blocker of human voltage-gated potassium channel (Kv)1.2 channels, with an IC50 of 160 pM, whereas its affinity for other channels tested was in the nanomolar range (hKv1.1, IC50 = 253 nM; hKv1.3, IC50 = 91 nM; and hKCa3.1, IC50 = 70 nM). The toxin had no effect on hKv1.4, hKv1.5, human ether-à-go-go–related gene type 1 (hERG1), or human ether-à-go-go–like (hELK2) channels. Multiple sequence alignments from the venom gland transcriptome showed the existence of four other new peptides similar to urotoxin. Computer modeling of urotoxin’s three-dimensional structure suggests the presence of the α/β-scaffold characteristic of other scorpion toxins, although very likely forming an uncommon disulfide pairing pattern. Using molecular dynamics, a model for the binding of this peptide to human Kv1.2 and hKv1.1 channels is presented, along with the binding of an in silico mutant urotoxin (Lys25Ala) to both channels. Urotoxin enriches our knowledge of K+ channel toxins and, due to its high affinity for hKv1.2 channels, it may be a good candidate for the development of pharmacologic tools to study the physiologic functions of K+ channels or related channelopathies and for restoring axonal conduction in demyelinated axons.
Footnotes
- Received October 8, 2013.
- Accepted April 10, 2014.
This work was supported by grants from the Dirección General de Asuntos del Personal Academico, UNAM [IN200113-3]; the Struan Sutherland Fund, AVRU, Department of Pharmacology and Therapeutics, University of Melbourne; a scholarship from CONACyT and from the Hugh Williamson Foundation, through the Museum Victoria; the European Union, and the State of Hungary, cofinanced by the European Social Fund in the framework of the National Excellence Program [TÁMOP 4.2.4. A/2-11-1-2012-0001] and [TÁMOP 4.2.2-A-11/1/KONV-2012-0025]; and the State of Hungary [OTKA K 75904] and [OTKA NK 101337]. The three-dimensional computer model of urotoxin and the brute force dynamic simulation was supported by a Victorian Life Sciences Computation Initiative (VLSCI) grant number [VR0064] at its Peak Computing Facility at the University of Melbourne, an initiative of the Victorian Government, Australia.
↵
This article has supplemental material available at molpharm.aspetjournals.org.
- Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics
MolPharm articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|