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Toxins 2017, 9(8), 248; doi:10.3390/toxins9080248

Lengths of the C-Terminus and Interconnecting Loops Impact Stability of Spider-Derived Gating Modifier Toxins

Institute for Molecular Bioscience, the University of Queensland, Brisbane, Queensland 4072, Australia
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Academic Editor: Steve Peigneur
Received: 17 July 2017 / Revised: 8 August 2017 / Accepted: 8 August 2017 / Published: 12 August 2017
(This article belongs to the Special Issue Toxins in Drug Discovery and Pharmacology)
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Abstract

Spider gating modifier toxins (GMTs) are potent modulators of voltage-gated ion channels and have thus attracted attention as drug leads for several pathophysiological conditions. GMTs contain three disulfide bonds organized in an inhibitory cystine knot, which putatively confers them with high stability; however, thus far, there has not been a focused study to establish the stability of GMTs in physiological conditions. We examined the resistance of five GMTs including GpTx-1, HnTx-IV, HwTx-IV, PaurTx-3 and SgTx-1, to pH, thermal and proteolytic degradation. The peptides were stable under physiological conditions, except SgTx-1, which was susceptible to proteolysis, probably due to a longer C-terminus compared to the other peptides. In non-physiological conditions, the five peptides withstood chaotropic degradation, and all but SgTx-1 remained intact after prolonged exposure to high temperature; however, the peptides were degraded in strongly alkaline solutions. GpTx-1 and PaurTx-3 were more resistant to basic hydrolysis than HnTx-IV, HwTx-IV and SgTx-1, probably because a shorter interconnecting loop 3 on GpTx-1 and PaurTx-3 may stabilize interactions between the C-terminus and the hydrophobic patch. Here, we establish that most GMTs are exceptionally stable, and propose that, in the design of GMT-based therapeutics, stability can be enhanced by optimizing the C-terminus in terms of length, and increased interactions with the hydrophobic patch. View Full-Text
Keywords: NaV1.7; nuclear magnetic resonance; pain; rational drug design; serum stability; spider venom NaV1.7; nuclear magnetic resonance; pain; rational drug design; serum stability; spider venom
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MDPI and ACS Style

Agwa, A.J.; Huang, Y.-H.; Craik, D.J.; Henriques, S.T.; Schroeder, C.I. Lengths of the C-Terminus and Interconnecting Loops Impact Stability of Spider-Derived Gating Modifier Toxins. Toxins 2017, 9, 248.

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