A K-BLOCKING PEPTIDE FROM VENOM OF CHINESE SCORPION BUTHUS-MARTENSII KARSCH( CHANNEL)

AIM: To purify and characterize a potassium channel blocker (BmP-3) fr om 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 e lectrospray ionization mass spectrometer. Amino acid composition was a nalyzed after acidic hydrolysis for 20 h in HCl 6 mol.L-1 at 110 degre es C. (2) Toxicity tests were conducted in mice and cockroaches. (3) T he inhibitory effects of BmP-3 on K+ channels were tested in acutely d issociated rat hippocampal pyramidal neurons using whole-cell patch-cl amp configuration. RESULTS: (1) A pure peptide (BmP-3, 8.1 mg) was obt ained, about 0.08 % of total proteins of the venom. The N-terminal seq uences were VGCEE and the molecular weight was 2938 in ESI-mass spectr a. (2) No death occurred at the dosage of 200 mu g in mice and 8 mu g in cockroaches. (3) The peptide at 10 mu mol.L-1 reduced the peak outw ard K+ currents by 63 % + 4 % in vitro. CONCLUSION: BmP-3 inhibited K channels.