Molecular cloning and sequencing of two ‘short chain’ and two ‘long chain’ K+ channel-blocking peptides from the Chinese scorpion Buthus martensii Karsch

AbstractFive full-length cDNAs encoding the precursors of two ‘short chain’ scorpion non-toxic peptides active on Ca2+-activated K+ channels (BmP02 and BmP03) and two novel putative long chain K+ channel-blocking peptides (named BmTXKβ and BmTXKβ2) were first isolated from the venom gland cDNA library of the Chinese scorpion Buthus martensii Karsch (BmK). BmTXKβ2 showed a high similarity with AaTXKβ, while BmTXKβ was completely different in the deduced primary structure from the long chain and short chain scorpion toxins already characterized. Thus, BmTXKβ expands the scorpion long chain K+ channel-blocking peptide family. Although little sequence similarity exists between the above two short and two long peptides, they are similar at the positions of six cysteines, suggesting that they should all share a similar scaffold composed of an α-helix and a three-stranded β-sheet