Gong Wu

Solution structure of BmKK2, a new potassium channel blocker from the venom of chinese scorpion Buthus martensi Karsch

A natural K+ channel blocker, BmKK2 (a member of scorpion toxin subfamily α‐KTx 14), which is composed of 31 amino acid residues and purified from the venom of the Chinese scorpion Buthus martensi Karsch, was characterized using whole‐cell patch‐clamp recording in rat hippocampal neurons. The three dimensional structure of BmKK2 was determined with two‐dimensional NMR spectroscopy and molecular modelling techniques. In solution this toxin adopted a common α/β‐motif, but showed distinct local conformation in the loop between α‐helix and β‐sheet in comparison with typical short‐chain scorpion toxins (e.g., CTX and NTX). Also, the α helix is shorter and the β‐sheet element is smaller (each strand consisted only two residues). The unusual structural feature of BmKK2 was attributed to the shorter loop between the α‐helix and β‐sheet and the presence of two consecutive Pro residues at position 21 and 22 in the loop. Moreover, two models of BmKK2/hKv1.3 channel and BmKK2/rSK2 channel complexes were simulated with docking calculations. The results demonstrated the existence of a α‐mode binding between the toxin and the channels. The model of BmKK2/rSK2 channel complex exhibited favorable contacts both in electrostatic and hydrophobic, including a network of five hydrogen bonds and bigger interface containing seven pairs of inter‐residue interactions. In contrast, the model of BmKK2/hKv1.3 channel complex, containing only three pairs of inter‐residue interactions, exhibited poor contacts and smaller interface. The results well explained its lower activity towards Kv channel, and predicted that it may prefer a type of SK channel with a narrower entryway as its specific receptor. Proteins 2004.

Purification, characterization and sequence determination of BmKK4, a novel potassium channel blocker from Chinese scorpion Buthus martensi Karsch.

The scorpion neurotoxin BmKK4 was purified from the venom of the Chinese scorpion Buthus martensi Karsch by a combination of gel-filtration, ion exchange and reversed phase chromatography. The primary sequence of BmKK4 was determined using the tandem MS/MS technique and the cDNA database searching as followings: ZTQCQ SVRDC QQYCL TPDRC SYGTC YCKTT (NH(2)). BmKK4 is the first isolated member of a new subfamily alpha-KTx17 of scorpion K(+) toxins.

The solution structure of BmTx3B, a member of the scorpion toxin subfamily α‐KTx 16

This article reports the solution structure of BmTx3B (α‐KTx16.2), a potassium channel blocker belonging to the subfamily α‐KTx16, purified from the venom of the Chinese scorpion Buthus martensi Karsch. In solution, BmTx3B assumes a typical CSαβ motif, with an α‐helix connected to a triple‐stranded β‐sheet by 3 disulfide bridges, which belongs to the first structural group of short‐chain scorpion toxins. On the other hand, BmTx3B is quite different from other toxins (such as ChTx and AgTx2) of this group in terms of the electrostatic and hydrophobic surface distribution. The functional surface (β‐face) of the molecule is characterized by less basic residues (only 2: Lys28 and Arg35) and extra aromatic residues (Phe1, Phe9, Trp15, and Tyr37). The peptide shows a great preference for the Kca1.1 channel over the Kv channel (about a 103‐fold difference). The model of BmTx3B/Kca1.1 channel complex generated by docking and dynamic simulation reveals that the stable binding between the BmTx3B and Kca1.1 channel is favored by a number of aromatic π–π stacking interactions. The influences of these structural features on the kinetic behavior of the toxin binding to Kca1.1 channel are also discussed. Proteins 2005.

BmKK4, a novel toxin from the venom of Asian scorpion Buthus martensi Karsch, inhibits potassium currents in rat hippocampal neurons in vitro.

A novel short-chain peptide BmKK4 was isolated from the venom of Asian scorpion Buthus martensi Karsch. It is composed of 30 amino acids including six cysteine residues, and shares less than 25% sequence identity with the known alpha-KTx toxins. The action of BmKK4 on voltage-dependent potassium currents was examined in acutely dissociated hippocampal neurons of rat. BmKK4 (10-100 microM) inhibited both the delayed rectifier and fast transient potassium current in concentration-dependent manners. The inhibition was reversible and voltage-independent. BmKK4 caused a depolarizing shift (about 10 mV) of the steady-state activation curve of the currents, without changing their steady-state inactivation behavior. The unique amino acid sequence and electrophysiological effects suggest that BmKK4 represent a new subfamily of potassium channel toxins.