BmBKTx1 is a 31-amino acid peptide identified from the venom of the Chinese scorpion
Buthus martensi Karsch, blocking high-conductance calcium-activated potassium channels. Sequencehomology analysis indicates that BmBKTx1 is a new subfamily of short-chain
-KTx toxins of thepotassium channel, which we term
-KTx19. Synthetic BmBKTx1 was prepared by using solid-phasepeptide synthesis. Two-dimensional NMR spectroscopy techniques were used to determine the solutionstructure of BmBKTx1. The results show that the BmBKTx1 forms a typical cysteine-stabilized
/
scaffoldadopted by most short-chain scorpion toxins. The structure of BmBKTx1 consists of a two-strandedantiparallel
-sheet (residues 20-29) and an
-helix (residues 5-15). The three-dimensional structure ofBmBKTx1 was also compared with those of two function-related scorpion toxins, charybdotoxin (ChTx)and BmTx1, and their structural and functional implications are discussed.