Purification and characterization of a new peptide with analgesic effect from the scorpion Buthus martensi Karch

A new peptide, designated as Buthus martensi Karch (BmK) AngM1, with an isoelectric point (pI) of 5.8 was purified and characterized from the venom of Buthus martensi Karch. The molecular mass was calculated as 7040.5 Da from multiple-charged ions by elelctrospray ionization mass spectroscopy (ESI/MS). The complete amino acid sequence of BmK AngM1 of 64 amino acid residues was determined by automatic sequencing of N-terminal part of the native peptide and the fragments of reduced and S-carboxymethylated (RCM)-peptide degraded by Staphylococcus aureaus V-8 protease and TPCK(N-p-Tosyl-L-phenylalanine chloromethyl ketone)-treated trypsin. Bioactivity tested using mouse-twisting model showed an evident analgesic effect with 63.0% (P < 0.001) inhibition efficiency at the dose of 0.8 mg/kg, but the LD50 was larger than 50 mg/kg. Electrophysiological studies showed that BmK AngM1 at the concentration of 1 muM obviously inhibit voltage-dependent Na+ current (I-Na) and voltage-dependent delayed rectifier K+ current (I-K) but had no effects on transient K+ current.