The isolation and characterization of a peptide that alters sodium channels from Buthus martensii Karsch

The peptides were purified using gel filtration, ion exchange, FPLC, and HP LC chromatography and found to greatly prolong action potentials at nanomol ar concentrations when applied to frog and mouse nerves. The N-terminal pri mary amino acid sequence of one of the peptides, BMK 16(5). was determined. The first 23 amino acids of BMK 16(5) were found to be: VKDGYIADDRNCPYFCGR NAYYD. The two cysteine residues in the sequence appeared as Edman sequence cycle blanks, however, they were assigned to be cysteines due to sequence similarity to other peptide toxins that bind to sodium channels and identif ication of the presence of cysteines obtained from single time point amino acid analysis. The MW of BMK 16(5) was determined by a Perkin-Elmer API 300 LC/MS/MS to be 3695, The amino acid residues of BMK 16(5) show strong simi larity with the first 23 amino acid residues of a number of scorpion alpha neurotoxins. Unlike these neurotoxins, BMK 16(5) possesses a proline residu e at position 13 which will likely make it fold in a unique way so as to bi nd to and alter sodium channels. (C) 1999 Elsevier Science Ltd. AII rights reserved.