Purification, characterization and 1H NMR resonance assignment of an α-like neurotoxin BmK 16 from the venom of Chinese scorpion Buthus martensii Karsch

A natural scorpion toxin BmK 16 was purified for the first time from the venom of the Chinese scorpion Buthus martensii Karsch (BmK) by using combined gel-filtration, ion exchange and reversed phase chromatography. The sequence of the N-terminal 8 amino acid residues was determined by Edman degradation. Using the N-terminal sequence as a tag, the database searching revealed a hit in the scorpion cDNA Bank. The sequence for N-terminal 8 amino acid residues, molecular weight and amino acid compositions of BmK 16 were identical with the calculated values according to the first 64 residues' sequence of the precursor peptide alpha-neurotoxin TX16 derived from the sequence of the cDNA AF156597 (EMBL). The sequence-specific resonance assignment of BmK 16 was achieved and the intact sequence of BmK 16 was determined as followings: VRDAY IAKPH NCVYE CARNE YCNDL CTKNG AKSGY CQWVG KYGNG CWCKE LPDNV PIRVP GKCH. Furthermore, the results from the sequence homology analysis and the toxicity assays indicated that BmK 16 was an alpha-like scorpion neurotoxin.