From the venom of scorpion Buthus martensii Karsch, a short peptide (BmP03, 28 amino acid residues) was isolated, characterized and tested as a weak inhibitor of K^+ channel. In this paper, the solution structure of BmP03 was determined by 2D ^1H NMR spectroscopy and molecular modeling calculations. The conformation of BmP03 is composed of a short α-helix (Cys3-Gly12) and a two-strand antiparallel β-sheet (Asn16-Cys19, Cys24-Asn27). There are three disulfide bridges (Cys3-Cys19, Cys6-Cys24, Cys10-cys26) connecting the α-helix and β-sheet. Asp20 to Val23 residues form a type Ⅱ turn linking the two strands. Structural and electrostatic potential comparison between BmP03 and its analogues were also presented.

Key words: NEUROTOXINS