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

Protx-i peptide,a venom toxin of the tarantula thrixopelma pruriens,has been reported to interact with voltage-gated ion channels. protx-i reduced ba2+ currents through recombinant human t-type voltage-gated ca2+ channels,cav3.1 (hcav3.1),with roughly 160-fold more potency than through hcav3.2 channels. chimeric channel proteins (hcav3.1/s3s4 and hcav3.2/ s3s4) were produced by exchanging fourteen amino acids in the hcav3.1 domain iv s3-s4 linker region and the corresponding region of hcav3.2 between each other. the protx-i sensitivity was markedly reduced in the hcav3.1/s3s4 chimera as compared to the original hcav3.1 channel,while the hcav3.2/s3s4 chimera exhibited greater protx-i sensitivity than the original hcav3.2 channel. these results suggest that the domain iv s3-s4 linker in the hcav3.1 channel may contain residues involved in the interaction of protx-i with t-type ca2+ channels. ©2010 the japanese pharmacological society.