APETx2, Anthopleura elegantissima, Recombinant, E. coli

Originally isolated from sea anemone Anthopleura elegantissima, the 42 amino-acid toxin APETx2 is shown to block acidification-induced activation of homotrimeric acid-sensing ion channel composed of rat or human ASIC3 (IC₅₀ against pH 7.4 to 6 ramping-induced transient current = 63 nM and 175 nM by whole-cell patch-clamp using COS cells expressing respective channel), but not rat ASIC1a, ASIC1b, or ASIC2a, in a reversible manner, presumably via its N-terminus interaction with type I β turn that connects β-strands I&II in the ASIC3 extracellular β-ball region. In addition to acidification-induced classical transient current, APETx2 is also shown to inhibit the Na⁺-dependent, alkalization-induced nonconventional channel activity seen in human, but not rat, ASIC3 (complete inhibition by 1 µM APETx3; pH 8.0). APETx2 in vivo efficacy is demonstrated in various rat pain induction models, including acid- (via calf i.m. injection of 100 µL pH 4.0 saline on day 1&5) induced mechanical hypersensitivity (pain withdrawal threshold = 76% and 24% of control rats with or without 100 µL 2.2 µM APETx2 i.m. injection prior to the second pH 4.0 saline injection). Although structurally related to known K⁺ channel modulators APETx1 and BDS-1/II, APETx2 is reported to display much reduced potency against Kv3.4 (38% inhibition by 3 µM APETx2) and little or no effect toward hERG, Kv2.2, Kv3.1, Kv4.2, or Kv4.3 channel activity.

Primary Target
ASIC3

Reversible: yes

Supplied as a trifluoroacetate salt.

Following reconstitution, aliquot and freeze (-20°C). Stock solutions are stable for up to 3 months at -20°C.

Delaunay, A., et al. 2012. Proc. Natl. Acad. Sci.109, 13124.
Sherwood, T.W., et al. 2012. Am. J. Physiol. Cell Physiol.303, C699.
Karczewski, J., et al. 2010. Br J Pharmacol.161, 950.
Chagot, B., et al. 2005. Protein Sci.14, 2003.

Diochot, S., et al. 2004. EMBO J.23, 1516.

H-Gly-Thr-Ala-Cys⁴-Ser-Cys⁶-Gly-Asn-Ser-Lys-Gly-Ile-Tyr-Trp-Phe-Tyr-Arg-Pro-Ser-Cys²⁰-Pro-Thr-Asp-Arg-Gly-Tyr-Thr-Gly-Ser-Cys³⁰-Arg-Tyr-Phe-Leu-Gly-Thr-Cys³⁷-Cys³⁸-Thr-Pro-Ala-Asp-OH (disulfide bonds: 4 → 37, 6 → 30, 20 → 38)

CALBIOCHEM is a registered trademark of Merck KGaA, Darmstadt, Germany

Toxicity: Standard Handling (A)