Cy5-ProTx-I

Cy5-ProTx-I (Protoxin 1; β-theraphotoxin-Tp1a) is a fluorescently labeled ProTx-I that was originally isolated from the venom of Thrixopelma pruriens (Peruvian green velvet tarantula). This toxin reversibly inhibits the tetrodotoxin (TTX)-resistant channel Na_v1.8 (IC₅₀ = 27 nM) and Na_v1.2, Na_v1.5 and Na_v1.7 with IC₅₀ values between 50 and 100 nM. Furthermore, ProTx-I shifts the voltage dependence activity of T-type Ca_v3.1 channels (IC₅₀= 50 nM) without affecting the voltage dependence of inactivation. ProTx-I is a valuable tool to discriminate between Ca_v3.1 and Ca_v3.2. ProTx-I is also an antagonist of TRAP1.