Blocker of voltage-gated sodium channels and T-type Cav

Protoxin I (ProTx-I; β-theraphotoxin-Tp1a) is a toxin that was originally isolated from the venom of Thrixopelma pruriens (Peruvian green velvet tarantula). This toxin reversibly inhibits the tetrodotoxin (TTX)-resistant channel Nav1.8(IC50 = 27 nM) and Nav1.2, Nav1.5 and Nav1.7 with IC50 values between 50 and 100 nM. Furthermore, ProTx-I shifts the voltage dependence activity of T-type Cav3.1 channels (IC50= 50 nM) without affecting the voltage dependence of inactivation. ProTx-I is a valuable tool to discriminate between Cav3.1 and Cav3.2


A, B, C, Recording traces of hNav1.7 current in the presence of Smartox sProTx-I (100 and 300 nM). The current was elicited by a 50 ms-depolarizing pulse to -10 mV from a holding potential of -90 mV. Inter-sweep period was 10 s. Current amplitudes were plotted against time. Black bar indicates toxin application. D, Families of hNav1.7 current traces in control and in the presence of 100 nM ProTx-I. Currents were evoked by depolarizing pulses from -60 mV to 40 mV, while the cell was hold at -90 mV. E, Amplitude-voltage relationships obtained from D.

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AA sequence: Glu-Cys2-Arg-Tyr-Trp-Leu-Gly-Gly-Cys9-Ser-Ala-Gly-Gln-Thr-Cys15-Cys16-Lys-His-Leu-Val-Cys21-Ser-Arg-Arg-His-Gly-Trp-Cys28-Val-Trp-Asp-Gly-Thr-Phe-Ser-OH
Disulfide bridges: Cys2-Cys16, Cys9-Cys21, Cys15-Cys28
Length (aa): 35
Formula: C171H245N53O47S6
Molecular Weight: 3987.50 Da
Appearance: White lyophilized solid
Solubility: water or saline buffer
CAS number: Not available
Source: Synthetic
Purity rate: > 95 %

Two tarantula peptides inhibit activation of multiple sodium channels

ProTx-I and ProTx-II: gating modifiers of voltage-gated sodium channels

Tarantula toxin ProTx-I differentiates between human T-type voltage-gated Ca2+ Channels Cav3.1 and Cav3.2

A Tarantula-Venom Peptide Antagonizes the TRPA1 Nociceptor Ion Channel by Binding to the S1-S4 Gating Domain