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8.B.12 The Spider Toxin (STx2) Family

Phoneutria nigriventer toxins, PnTx2-5 and PnTx2-6, markedly delay the fast inactivation kinetics of neuronal-type sodium channels, but they have differences in their interactions with the channel (Matavel et al., 2009). PnTx2-6 has an affinity 6 times higher than that of PnTx2-5, and its effects are not reversible within 10-15 min of washing. PnTx2-6 partially (59%) competes with the scorpion alpha-toxin AaHII, but not with the scorpion beta-toxin CssIV, thus suggesting a mode of action similar to that of site 3 toxins. However, PnTx2-6 is not removed by strong depolarizing pulses, as in the known site 3 toxins. Matavel et al., 2009 also established that the cysteines in these poorly helical toxins are in their oxidized form.

This family belongs to the: Huwentoxin Superfamily.

References associated with 8.B.12 family:

Liu, Z., J. Dai, L. Dai, M. Deng, Z. Hu, W. Hu, and S. Liang. (2006). Function and solution structure of Huwentoxin-X, a specific blocker of N-type calcium channels, from the Chinese bird spider Ornithoctonus huwena. J. Biol. Chem. 281: 8628-8635. 16439354
Matavel, A., C. Fleury, L.C. Oliveira, F. Molina, M.E. de Lima, J.S. Cruz, M.N. Cordeiro, M. Richardson, C.H. Ramos, and P.S. Beirão. (2009). Structure and activity analysis of two spider toxins that alter sodium channel inactivation kinetics. Biochemistry 48: 3078-3088. 19231838