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Diverse Structural Features of Potassium Channels Characterized by Scorpion Toxins as Molecular Probes.

ABSTRACT: Scorpion toxins are well-known as the largest potassium channel peptide blocker family. They have been successfully proven to be valuable molecular probes for structural research on diverse potassium channels. The potassium channel pore region, including the turret and filter regions, is the binding interface for scorpion toxins, and structural features from different potassium channels have been identified using different scorpion toxins. According to the spatial orientation of channel turrets with differential sequence lengths and identities, conformational changes and molecular surface properties, the potassium channel turrets can be divided into the following three states: open state with less hindering effects on toxin binding, half-open state or half-closed state with certain effects on toxin binding, and closed state with remarkable effects on toxin binding. In this review, we summarized the diverse structural features of potassium channels explored using scorpion toxin tools and discuss future work in the field of scorpion toxin-potassium channel interactions.

SUBMITTER: Zhao Y

PROVIDER: S-EPMC6600638 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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Diverse Structural Features of Potassium Channels Characterized by Scorpion Toxins as Molecular Probes.

Zhao Yonghui Y Chen Zongyun Z Cao Zhijian Z Li Wenxin W Wu Yingliang Y

Molecules (Basel, Switzerland) 20190529 11

Scorpion toxins are well-known as the largest potassium channel peptide blocker family. They have been successfully proven to be valuable molecular probes for structural research on diverse potassium channels. The potassium channel pore region, including the turret and filter regions, is the binding interface for scorpion toxins, and structural features from different potassium channels have been identified using different scorpion toxins. According to the spatial orientation of channel turrets ...[more]

PMID: 31146335

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Project description:?-Scorpion toxins constitute a family of peptide modulators that induce a prolongation of the action potential of excitable cells by inhibiting voltage-gated sodium channel inactivation. Although they all adopt a conserved structural scaffold, the potency and phylogentic preference of these toxins largely vary, which render them an intriguing model for studying evolutionary diversification among family members. Here, we report molecular characterization of a new multigene family of ?-toxins comprising 13 members (named MeuNaTx?-1 to MeuNaTx?-13) from the scorpion Mesobuthus eupeus. Of them, five native toxins (MeuNaTx?-1 to -5) were purified to homogeneity from the venom and the solution structure of MeuNaTx?-5 was solved by nuclear magnetic resonance. A systematic functional evaluation of MeuNaTx?-1, -2, -4, and -5 was conducted by two-electrode voltage-clamp recordings on seven cloned mammalian voltage-gated sodium channels (Na(v)1.2 to Na(v)1.8) and the insect counterpart DmNa(v)1 expressed in Xenopus oocytes. Results show that all these four peptides slow inactivation of DmNa(v)1 and are inactive on Na(v)1.8 at micromolar concentrations. However, they exhibit differential specificity for the other six channel isoforms (Na(v)1.2 to Na(v)1.7), in which MeuNaTx?-4 shows no activity on these isoforms and thus represents the first Mesobuthus-derived insect-selective ?-toxin identified so far with a half maximal effective concentration of 130 ± 2 nm on DmNa(v)1 and a half maximal lethal dose of about 200 pmol g(-1) on the insect Musca domestica; MeuNaTx?-2 only affects Na(v)1.4; MeuNaTx?-1 and MeuNaTx?-5 have a wider range of channel spectrum, the former active on Na(v)1.2, Na(v)1.3, Na(v)1.6, and Na(v)1.7, whereas the latter acting on Na(v)1.3-Na(v)1.7. Remarkably, MeuNaTx?-4 and MeuNaTx?-5 are two nearly identical peptides differing by only one point mutation at site 50 (A50V) but exhibit rather different channel subtype selectivity, highlighting a switch role of this site in altering the target specificity. By the maximum likelihood models of codon substitution, we detected nine positively selected sites (PSSs) that could be involved in functional diversification of Mesobuthus ?-toxins. The PSSs include site 50 and other seven sites located in functional surfaces of ?-toxins. This work represents the first thorough investigation of evolutionary diversification of ?-toxins derived from a specific scorpion lineage from the perspectives of sequence, structure, function, and evolution.

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Diverse Structural Features of Potassium Channels Characterized by Scorpion Toxins as Molecular Probes.

Publications

Diverse Structural Features of Potassium Channels Characterized by Scorpion Toxins as Molecular Probes.

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