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Crystal structure of tarantula venom peptide Protoxin-II
Structural highlights
FunctionTXPR2_THRPR Blocks both tetrodotoxin-sensitive and tetrodotoxin-resistant human voltage-gated sodium channels by shifting the voltage dependence of channel activation to more positive potentials. Inhibits Nav1.2/SCN2A, Nav1.3/SCN3A, Nav1.5/SCN5A, Nav1.6/SCN8A, Nav1.7/SCN9A, Nav1.8/SCN10A. Is significantly more potent against Nav1.7/SCN9A than the other Nav channel subtypes. Has no significant effect on Kv1.2/KCNA2, Kv1.3/KCNA3, Kv1.5/KCNA5, and Kv2.1/KCNB1 channels. Also inhibits Cav1.2/CACNA1C and Cav3.1/CACNA1G channels with an IC(50) around 100 nM. Does not bind to the pharmacologically defined Nav channel sites 3 or 4. Neutralization of gating charges in the voltage sensor (S4) of domain II of Nav1.2/SCN2A prevents the effect of the toxin on gating current. Thus, it has been suggested that the toxin acts by trapping the voltage sensor of Nav channel domain II in the resting state, impeding outward gating movement of the IIS4 transmembrane segment of the channel. Binds to phospholipids.[1] [2] [3] [4] [5] [6] Publication Abstract from PubMedSpider venom toxins, such as Protoxin-II (ProTx-II), have recently received much attention as selective Nav1.7 channel blockers, with potential to be developed as leads for the treatment of chronic nocioceptive pain. ProTx-II is a 30-amino acid peptide with three disulfide bonds that has been reported to adopt a well-defined inhibitory cystine knot (ICK) scaffold structure. Potential drawbacks with such peptides include poor pharmacodynamics and potential scrambling of the disulfide bonds in vivo. In order to address these issues, in the present study we report the solid-phase synthesis of lanthionine-bridged analogues of ProTx-II, in which one of the three disulfide bridges is replaced with a thioether linkage, and evaluate the biological properties of these analogues. We have also investigated the folding and disulfide bridging patterns arising from different methods of oxidation of the linear peptide precursor. Finally, we report the X-ray crystal structure of ProTx-II to atomic resolution; to our knowledge this is the first crystal structure of an ICK spider venom peptide not bound to a substrate. The Role of Disulfide Bond Replacements in Analogues of the Tarantula Toxin ProTx-II and Their Effects on Inhibition of the Voltage-Gated Sodium Ion Channel Nav1.7.,Wright ZVF, McCarthy S, Dickman R, Reyes FE, Sanchez-Martinez S, Cryar A, Kilford I, Hall A, Takle AK, Topf M, Gonen T, Thalassinos K, Tabor AB J Am Chem Soc. 2017 Sep 20;139(37):13063-13075. doi: 10.1021/jacs.7b06506. Epub, 2017 Sep 7. PMID:28880078[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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