title: Elucidation of the molecular basis of selective recognition uncovers the interaction site for the core domain of scorpion alpha-toxins on sodium channels.
abstract: Neurotoxin receptor site-3 at voltage-gated Na(+) channels is recognized by various peptide toxin inhibitors of channel inactivation. Despite extensive studies of the effects of these toxins, their mode of interaction with the channel remained to be described at the molecular level. To identify channel constituents that interact with the toxins, we exploited the opposing preferences of LqhαIT and Lqh2 scorpion α-toxins for insect and mammalian brain Na(+) channels. Construction of the DIV/S1-S2, DIV/S3-S4, DI/S5-SS1, and DI/SS2-S6 external loops of the rat brain rNa(v)1.2a channel (highly sensitive to Lqh2) in the background of the Drosophila DmNa(v)1 channel (highly sensitive to LqhαIT), and examination of toxin activity on the channel chimera expressed in Xenopus oocytes revealed a substantial decrease in LqhαIT effect, whereas Lqh2 was as effective as at rNa(v)1.2a. Further substitutions of individual loops and specific residues followed by examination of gain or loss in Lqh2 and LqhαIT activities highlighted the importance of DI/S5-S6 (pore module) and the C-terminal region of DIV/S3 (gating module) of rNa(v)1.2a for Lqh2 action and selectivity. In contrast, a single substitution of Glu-1613 to Asp at DIV/S3-S4 converted rNa(v)1.2a to high sensitivity toward LqhαIT. Comparison of depolarization-driven dissociation of Lqh2 and mutant derivatives off their binding site at rNa(v)1.2a mutant channels has suggested that the toxin core domain interacts with the gating module of DIV. These results constitute the first step in better understanding of the way scorpion α-toxins interact with voltage-gated Na(+)-channels at the molecular level.
authors.affiliation: Department of Plant Molecular Biology and Ecology, George S Wise Faculty of Life Sciences, Tel-Aviv University, Ramat-Aviv, Tel-Aviv 69978, Israel.
authors.forename: Maya
authors.initials: M
authors.lastname: Gur
authors.forename: Roy
authors.initials: R
authors.lastname: Kahn
authors.forename: Izhar
authors.initials: I
authors.lastname: Karbat
authors.forename: Noa
authors.initials: N
authors.lastname: Regev
authors.forename: Jinti
authors.initials: J
authors.lastname: Wang
authors.forename: William A
authors.initials: WA
authors.lastname: Catterall
authors.forename: Dalia
authors.initials: D
authors.lastname: Gordon
authors.forename: Michael
authors.initials: M
authors.lastname: Gurevitz
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004330:Drosophila; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D009498:Neurotoxins / Q000378:metabolism; D051381:Rats; D012604:Scorpion Venoms / Q000378:metabolism*; D012605:Scorpions / Q000378:metabolism*; D012615:Sea Anemones; D017386:Sequence Homology, Amino Acid; D015222:Sodium Channels / Q000737:chemistry*; D014981:Xenopus
chemical_list: D018076:DNA, Complementary; D009498:Neurotoxins; D012604:Scorpion Venoms; D015222:Sodium Channels