GsAF-II (also termed Kappa-theraphotoxin-Gr2c, GsAF-2) was originally isolated from the venom of Grammostola rosea spider. GsAF-II peptide toxin has antinociceptive and antiarrhythmic effects in mammals. The peptide is reported to block the following voltage-gated sodium channels: Na_v1.1, Na_v1.2, Na_v1.3, Na_v1.4, Na_v1.6 and Na_v1.7 with IC₅₀ values of, respectively, 5.7, 12, 24, 4, 6.6 and 1.3 µM. This peptide also blocks hERG1 with an IC₅₀ value of 4.7 µM.

Description:

AA sequence: Tyr-Cys²-Gln-Lys-Trp-Met-Trp-Thr-Cys⁹-Asp-Glu-Glu-Arg-Lys-Cys¹⁵-Cys¹⁶-Glu-Gly-Leu-Val-Cys²¹-Arg-Leu-Trp-Cys²⁵-Lys-Lys-Lys-Ile-Glu-Trp-OHDisulfide bonds: Cys²-Cys¹⁶, Cys⁹-Cys²¹, and Cys¹⁵-Cys²⁵)Length (aa): 31Formula: C₁₇₆H₂₆₁N₄₇O₄₅S₇Molecular Weight:  3979.78 DaAppearance: White lyophilized solidSolubility: aqueous bufferCAS number: not availableSource: SyntheticPurity rate: > 98%

Reference:

Target Promiscuity and Heterogeneous Effects of Tarantula Venom Peptides Affecting Na⁺ and K⁺ Ion Channels

Venom-derived peptide modulators of ion channel gating are regarded as essential tools for understanding the molecular motions that occur during the opening and closing of ion channels. In this study, we present the characterization of five spider toxins on 12 human voltage-gated ion channels, following observations about the target promiscuity of some spider toxins and the ongoing revision of their “canonical” gating-modifying mode of action. The peptides were purified de novo from the venom of Grammostola rosea tarantulas, and their sequences were confirmed by Edman degradation and mass spectrometry analysis. Their effects on seven tetrodotoxin-sensitive Na(+) channels, the three human ether-à-go-go (hERG)-related K(+) channels, and two human Shaker-related K(+) channels were extensively characterized by electrophysiological techniques. All thepeptides inhibited ion conduction through all the Na(+) channels tested, although with distinctive patterns. The peptides also affected the three pharmaceutically relevant hERG isoforms differently. At higher concentrations, all peptides also modified the gating of the Na(+) channels by shifting the activation to more positive potentials, whereas more complex effects were recorded on hERG channels. No effects were evident on the two Shaker-related K(+) channels at concentrations well above the IC(50) value for the affected channels. Given the sequence diversity of the testedpeptides, we propose that tarantula toxins should be considered both as multimode and target-promiscuous ion channel modulators; both features should not be ignored when extracting mechanistic interpretations about ion channel gating. Our observations could also aid in future structure-function studies and might help the development of novel ion channel-specific drugs.

Elisa Redaelli, et al. (2010) Target Promiscuity and Heterogeneous Effects of Tarantula Venom Peptides Affecting Na⁺ and K⁺ Ion Channels. JBC. PMID: 19955179

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