RhTx
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RhTx is a small peptide toxin from Scolopendra subspinipes mutilans, also called the Chinese red-headed centipede. RhTx binds to the outer pore region of the temperature regulated TRPV1 ion channel, preferably in activated state, causing a downwards shift in the activation threshold temperature, which leads to the immediate onset of heat pain.[1]
RhTx is a component of the venom of the S. subspinipes mutilans, also called the Chinese red-headed centipede.[1]
Chemistry
RhTx is a small peptide toxin, with a compact 3D-structure. The gene encoding for RhTx translates into a 69 amino acid peptide that shows no homology to any known animal toxin. This peptide, after post- translational modifications, yields a mature toxin of 27 amino acids. RhTx has two pairs of disulfide bonds. While the N-terminus of the peptide contains no charged amino acids, the C-terminus of the peptide is rich in charged amino acids. In the folded peptide, these charged amino acids are all located on the same side of the peptide, making RhTx a polar molecule.[1]
Target
RhTx binds to the outer pore region of the polymodal TRPV1 ion channel. The toxin preferably binds to TRPV1 in the activated state of the channel. RhTx has a high affinity for the TRPV1 ion channel, which results in very rapid binding and slow unbinding. The TRPV1 channel is a non-selective cation channel, with a high permeability to Ca2+.[2] TRPV1 is mainly expressed in sensory neurons and can be activated by different stimuli, including high temperatures (heat), acids, pollutants with negative electric charge and endogenous metabolites such as anandamide.[3] The channel is also targeted by the active component of chilli peppers capsaicin, and the spider toxins Vanillotoxin and DkTx.[3][4][5]