Wu B., et al (2016), Toxins; PMID: 27690098 BmP02, a short-chain peptide with 28 residues from the venom of Chinese scorpion Buthus martensi Karsch, has been reported to inhibit the transient outward potassium currents (I_to) in rat ventricular muscle cells. However, it remains unclear whether BmP02 modulates the Kv4.2 channel, one of the main contributors to I_to. The present study investigated the effects of BmP02 on Kv4.2 kinetics and its underlying molecular mechanism. The electrophysiological recordings showed that the inactivation of Kv4.2 expressed in HEK293T cells was significantly delayed by BmP02 in a dose-response manner with EC₅₀ of ~850 nM while the peak current, activation and voltage-dependent inactivation of Kv4.2 were not affected. Meanwhile, the recovery from inactivation of Kv4.2 was accelerated and the deactivation was slowed after the application of BmP02. The site-directed mutagenesis combined with computational modelling identified that K347 and K353, located in the turret motif of the Kv4.2, and E4/E5, D20/D21 in BmP02 are key residues to interact with BmP02 through electrostatic force. These findings not only reveal a novel interaction between Kv4.2 channel and its peptidyl modulator, but also provide valuable information for design of highly-selective Kv4.2 modulators.

Wu B., et al (2016), Sci Rep. PMID: 27403813 The potassium channel Kv 1.3 plays a vital part in the activation of T lymphocytes and is an attractive pharmacological target for autoimmune diseases. BmP02, a 28-residue peptide isolated from Chinese scorpion (Buthus martensi Karsch) venom, is a potent and selective Kv1.3 channel blocker. However, the mechanism through which BmP02 recognizes and inhibits the Kv1.3 channel is still unclear. In the present study, a complex molecular model of Kv1.3-BmP02 was developed by docking analysis and molecular dynamics simulations. From these simulations, it appears the large β-turn (residues 10-16) of BmP02 might be the binding interface with Kv 1.3. These results were confirmed by scanning alanine mutagenesis of BmP02, which identified His9, Lys11 and Lys13, which lie within BmP02’s β-turn, as key residues for interacting with Kv1.3. Based on these results and molecular modeling, two negatively charged residues of Kv1.3, D421 and D422, located in turret region, were predicted to act as the binding site for BmP02. Mutation of these residues reduced sensitivity of Kv 1.3 to BmP02 inhibition, suggesting that electrostatic interactions play a crucial role in Kv1.3-BmP02 interaction. This study revealed the molecular basis of Kv 1.3 recognition by BmP02 venom, and provides a novel interaction model for Kv channel-specific blocker complex, which may help guide future drug-design for Kv1.3-related channelopathies.

Xu Y., et al (2000). PMID: 11076505 BmP02 is a 28-amino acid residue peptide purified from the venom of the Chinese scorpion Buthus martensi Karsch, which had been demonstrated to be a weak blocker of apamin-sensitive calcium-activated potassium channels. Two-dimensional NMR spectroscopy techniques were used to determine the solution structure of BmP02. The results show that BmP02 formed a alpha/beta scorpion fold, the typical three-dimensional structure adopted by most short chain scorpion toxins whose structures have been determined. However, in BmP02 this alpha/beta fold was largely distorted. The alpha-helix was shortened to only one turn, and the loop connecting the helix to the first beta-strand exhibited conformational heterogeneity. The instability of BmP02 could be attributed to a proline at position 17, which is usually a glycine. Because the residue at this position makes intense contact with the alpha-helix, it was supposed that the bulky side chain of proline had pushed the helix away from the beta-sheet. This had a significant influence on the structure and function of BmP02. The alpha-helix rotated by about 40 degrees to avoid Pro17 while forming two disulfides with the second beta-strand. The rotation further caused both ends of the helix to be unwound due to covalent restrictions. According to its structure, BmP02 was supposed to interact with its target via the side chains of Lys11 and Lys13.

Romi-Lebrun R., et al. (1997). Eur J Biochem. PMID: 9151979

Four peptidyl inhibitors of the small-conductance Ca2+-activated K+ channels (SK(Ca)) have been isolated from the venom of the Chinese scorpion Buthus martensi. These peptides were identified by screening C18 HPLC fractions of the crude venom by means of mass analysis by matrix-assisted-laser-desorption/ionization time-of-flight mass spectrometry, and toxicological tests in mice. Edman degradation analysis of the purified peptides showed sequences of 28-31 amino acids including 6 cysteine residues. Three of the sequences were similar to the P01 peptides from Androctonus scorpions, showing 76% sequence similarity for the most closely related, named BmP01, and 46% for the other two, named BmP02 and BmP03. Like the P01 peptides, these molecules showed a low toxic activity in mice after intracerebroventricular injection, and competed (K0.5 > 1 microM) with iodinated apamin for binding to its receptor site from rat brain, which has been proved to be the SK(Ca) channels. The fourth toxin was structurally related to the P05/leiurotoxin I toxin family, with 90% similarity, and was named BmP05. This toxin exhibited a high toxic activity with lethal effects in mice. Due to its small representation in the venom [less than 0.01% (by mass)], its biological properties have been assessed on the synthetic analogue of BmP05, which was assembled on a solid phase by means of Fmoc methodology. The synthetic peptide was physicochemically identical to the natural peptide, as shown by comparison of their molecular masses and amino acid compositions, and by their coelution after coinjection on capillary electrophoresis. These results confirmed the primary structure of BmP05 including an amidated C-terminus. Similarly to natural BmP05, synthetic BmP05 produced toxic and lethal effects after intracerebroventricular injection in mice (LD50 = 37 ng), and was able to compete with iodinated apamin for binding to its receptor in rat brain (K0.5 = 20 pM).