Download MendeleyA sodium channel inhibitor ISTX-I with a novel structure provides a new hint at the evolutionary link between two toxin folds.
Rong, M., Liu, J., Zhang, M., Wang, G., Zhao, G., Wang, G., Zhang, Y., Hu, K., Lai, R.(2016) Sci Rep 6: 29691-29691
- PubMed: 27407029
- DOI: https://doi.org/10.1038/srep29691
- Primary Citation of Related Structures:
2NDI - PubMed Abstract:
Members of arachnida, such as spiders and scorpions, commonly produce venom with specialized venom glands, paralyzing their prey with neurotoxins that specifically target ion channels. Two well-studied motifs, the disulfide-directed hairpin (DDH) and the inhibitor cystine knot motif (ICK), are both found in scorpion and spider toxins. As arachnids, ticks inject a neurotoxin-containing cocktail from their salivary glands into the host to acquire a blood meal, but peptide toxins acting on ion channels have not been observed in ticks. Here, a new neurotoxin (ISTX-I) that acts on sodium channels was identified from the hard tick Ixodes scapularis and characterized. ISTX-I exhibits a potent inhibitory function with an IC50 of 1.6 μM for sodium channel Nav1.7 but not other sodium channel subtypes. ISTX-I adopts a novel structural fold and is distinct from the canonical ICK motif. Analysis of the ISTX-I, DDH and ICK motifs reveals that the new ISTX-I motif might be an intermediate scaffold between DDH and ICK, and ISTX-I is a clue to the evolutionary link between the DDH and ICK motifs. These results provide a glimpse into the convergent evolution of neurotoxins from predatory and blood-sucking arthropods.
Organizational Affiliation:
Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences &Yunnan Province, Kunming Institute of Zoology, Kunming Yunnan 650223, China.
