A K^+ channel-blocking peptide from venom of Chinese scorpion Buthus martensii Karsch

A K + channel blocking peptide from venom of Chinese scorpion Buthus martensii Karsch 1

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AIM: To purify and characterize a potassium channel blocker ( Bm P 3) from the venom of Chinese scorpion Buthus martensii Karsch. METHODS: ① Purification was carried out by gel filtration, cation exchange, and reversed phase chromatographies. N terminal was directly sequenced by double coupling manual method. Molecular weight was determined on an electrospray ionization mass spectrometer. Amino acid composition was analyzed after acidic hydrolysis for 20 h in HCl 6 mol·L -1 at 110 ℃. ②Toxicity tests were conducted in mice and cockroaches. ③The inhibitory effects of Bm P 3 on K + channels were tested in acutely dissociated rat hippocampal pyramidal neurons using whole cell patch clamp configuration. RESULTS: ① A pure peptide ( Bm P 3, 8 1 mg) was obtained, about 0.08 % of total proteins of the venom. The N terminal sequences were VGCEE and the molecular weight was 2938 in ESI mass spectra. ② No death occurred at the dosage of 200 μg in mice and 8 μg in cockroaches. ③The peptide at 10 μmol·L -1 reduced the peak outward K + currents by 63 %±4 % in vitro . CONCLUSION: Bm P 3 inhibited K + channels.