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Protein dynamic networks play an important role in the regulation of many protein systems. Some residues that are far away from the interface between proteins and their targets have a critical role in modulating the activity of some scorpion toxins. Here, conservation analysis combined with an in vivo experiment has reveals that Met58 is a key residue of BmK scorpion toxin AGP-SYPU2 in the modulation of analgesic activity. Molecular dynamics simulations clearly reveal the conformational changes that allow the loop between the β2 and β3 sheets to be exposed on the toxin surface to interact with its targets. Our results emphasize specific roles for the residue Met58 in the NC domain and our work gives valuable information for further modification of scorpion toxins to obtain new analgesic peptides with enhanced activity. Communicated by Ramaswamy H. Sarma.

Scorpion venom is composed of a large number of bioactive peptides which display important pharmacological activities. In this study we have carried out a study of the functional role of the arginine residue at position 58 in the site RC comprising the reverse turn (8-12) and C-terminal residues 58-64. A polymerase chain reaction was used to substitute this arginine residue with a single amino acid such as alanine, glycine and lysine. The mutants were expressed in soluble form in E. coli, and purified by affinity chromatography. After target peptide purity identification, the recombinant peptides underwent a circular dichroism analysis and a study of their analgesic activity in mice. The results indicated that a single residue modification can affect the pharmacological activity. Our efforts establish a sound basis for further study of the structure-function determinants of the analgesic effect., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Scorpion toxins are invaluable source of therapeutic leads and pharmacological tools which produce influence on the voltage gated sodium channels. In the previous study, our group has reported BmK AGP-SYPU1 (64 amino acids), one scorpion toxin with both potential α-type and β-type scorpion characteristics and analgesic activity in vivo, act as an activator to hNa v 1.4 and hNa v 1.5. Additionally, conserved aromatic amino acids Tyr5 and Tyr42 played important roles in bioactivity of BmK AGP-SYPU1 on hNa v 1.4 and hNa v 1.5. However, the anti-nonceptitor mechanisms of BmK AGP-SYPU1 referred in vivo have not been clarified yet. The roles of Tyr5 and Tyr42 have still kept unclear in the interaction of BmK AGP-SYPU1 with other VGSCs. In this study, in order to give a deep insight into the relationship of structure and function, the effects of BmK AGP-SYPU1 and its two mutants (Y5F and Y42F) on hNa v 1.7, which has emerged as a key molecule involved in pain processing, were examined by using Na + -specialized fluorescent dye and the whole-cell patch clamp. The data showed that BmK AGP-SYPU1 also displayed as an activator to hNa v 1.7 with the potential characteristic of α-type and β-type scorpion toxin. Both Tyr5 and Tyr42 were the key amino acids to the functional properties of BmK AGP-SYPU1 when interacting with hNa v 1.7, and the Tyr42 was involved in the preferences of the toxin to distinct action sites of hNa v 1.7. On the whole, these data provided more information about the structure of BmK AGP-SYPU1 related to its function upon hNa v 1.7, and may bring some clues for engineering scorpion toxins to achieve high bioactivity with lower side effects., (Copyright © 2017. Published by Elsevier B.V.)

The genomic DNA sequence encoding an antitumor-analgesic peptide was amplified from the genome of Chinese scorpion Buthus martensii Karsch (BmKAGAP), then cloned and sequenced. An intron, with a high A + T content (61.6%), splits a glycine codon near the end of the precursor signal peptide and the consensus GT/AG splice junction was identified in the BmKAGAP gene. Using PCR amplification, we confirmed the identity of our cloned cDNA, and found that the BmKAGAP gene contained an intron of 506 bp in length, which was almost identical to that of the characterized scorpion sodium channel ligands in size, consensus junctions, putative branch point and A + T content. This is the first report of using a statistical method for Chinese scorpion B. martensii Karsch genomic sequence analysis, involving the extraction of some putative transcription regulatory factors. Moreover, it establishes a theoretical foundation for studying the relationship between scorpion evolution, gene expression and protein function., (Copyright 2010 Elsevier Ltd. All rights reserved.)

The scorpion Buthus martensii Karsch (BmK) has been one of the indispensable materials in Chinese traditional medicine for thousands of years. In this work, an analgesic peptide was purified through four continuous chromatographic steps. The mouse twisting test was used to identify the target peptides in every separation step. The molecular weight, isoelectric point, and N-terminal residues of the purified peptide were determined. Based on the N-terminal sequence, the cDNA was also cloned by rapid amplification of cDNA ends from the cDNA pool of scorpion glands. This peptide was identical to BmK AS, an agonist of rabbit skeletal muscle ryanodine receptors. Preliminary pharmacodynamics revealed the following: the dose-effect curve plotted by the mouse twisting test showed an ED(50) of 1.42 mg/kg; and the time-effect curves plotted by a hot plate procedure showed a similar effect to the painkiller morphine. We report a purification procedure that yields substantial amounts of natural BmK AS having high activity. BmK AS has the potential to become a new analgesic medicine.

Anti-tumour-analgesic peptide (AGAP), one scorpion toxin purified from Buthus martensii Karsch, was known as its analgesic and anti-tumour activities. Trp38, a conserved aromatic residue of AGAP, might play important roles in its interaction with sodium channels. In this study, a mutant W38F was generated and effects of W38F were examined on hNav1.4, hNav1.5 and hNav1.7 by using whole-cell patch-clamp, which were closely associated to the biotoxicity of skeletal and cardiac muscles and pain signalling. The data showed that W38F decreased the inhibition effects of peak currents of hNav1.7, hNav1.4 and hNav1.5 compared with AGAP, notably, W38F reduced the analgesic activity compared with AGAP. The results suggested that Trp38 be a crucial amino acid involved in the interaction with these three sodium channels. The decreased analgesic activity of W38F might result from its much less inhibition of hNav1.7. These findings provided more information about the relationship between structure and function of AGAP and may facilitate the modification of other scorpion toxins with pharmacological effects. [ABSTRACT FROM AUTHOR]