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The redescriptions and illustrations of three species, Isometrus (Isometrus) maculatus (DeGeer, 1778), Lychas mucronatus (Fabricius, 1798) (Buthidae), and Liocheles australasiae (Fabricius, 1775) (Hemiscorpiidae) from Hainan Island, China are presented. Distribution data and updated key of Hainan scorpions are provided. [ABSTRACT FROM AUTHOR]

Background: Although the basic scorpion K+ channel toxins (KTxs) are well-known pharmacological tools and potential drug candidates, characterization the acidic KTxs still has the great significance for their potential selectivity towards different K+ channel subtypes. Unfortunately, research on the acidic KTxs has been ignored for several years and progressed slowly. Principal Findings: Here, we describe the identification of nine new acidic KTxs by cDNA cloning and bioinformatic analyses. Seven of these toxins belong to three new α-KTx subfamilies (α-KTx28, α-KTx29, and α-KTx30), and two are new members of the known k-KTx2 subfamily. ImKTx104 containing three disulfide bridges, the first member of the α-KTx28 subfamily, has a low sequence homology with other known KTxs, and its NMR structure suggests ImKTx104 adopts a modified cystine-stabilized α-helix-loop-β -sheet (CS-α/β) fold motif that has no apparent α-helixs and β-sheets, but still stabilized by three disulfide bridges. These newly described acidic KTxs exhibit differential pharmacological effects on potassium channels. Acidic scorpion toxin ImKTx104 was the first peptide inhibitor found to affect KCNQ1 channel, which is insensitive to the basic KTxs and is strongly associated with human cardiac abnormalities. ImKTx104 selectively inhibited KCNQ1 channel with a Kd of 11.69 μM, but was less effective against the basic KTxs-sensitive potassium channels. In addition to the ImKTx104 toxin, HeTx204 peptide, containing a cystine-stabilized α-helix-loop-helix (CS-α/α) fold scaffold motif, blocked both Kv1.3 and KCNQ1 channels. StKTx23 toxin, with a cystine-stabilized α-helix-loop-β-sheet (CS-α /β) fold motif, could inhibit Kv1.3 channel, but not the KCNQ1 channel. Conclusions/Significance: These findings characterize the structural and functional diversity of acidic KTxs, and could accelerate the development and clinical use of acidic KTxs as pharmacological tools and potential drugs. [ABSTRACT FROM AUTHOR]

The gene encoding the BmαTX14 (α-neurotoxin TX14) protein, derived from the cDNA library of the Chinese scorpion Buthus martensii Karsch, was expressed in Pichia pastoris. The recombinant protein was purified by metal chelate affinity chromatography and gel filtration chromatography. Using patch-clamp technique, electrophysiological activity of rBmαTX14 was identified. In the neurons isolated from mice trigeminal root ganglion, the Na+ current amplitude was reduced by 80% under whole cell patch-clamp recording. There were no apparent modifications to the gating mechanism in the presence of rBmαTX14. Although BmαTX14 shared a high amino acid sequence similarity with other typical α-toxins, it has different effects on neurons. Further electrophysiological analysis suggested that rBmαTX14 selectively blocked Na+ channels and is a member of a new group of scorpion toxins. [ABSTRACT FROM AUTHOR]