The blocking effect of BmP02, one novel short-chain scorpion peptide on transient outward K+ channel of adult rat ventricular myocyte

Two components F-2-7-4 and F-2-7-5, each composed of 28 amino acid residues , were purified from the venom of Buthus martensi Karsch by an opportune pr ocedure with cation-exchange column chromatography and repeated HPLC. Both components were totally accounted to about 0.88% dry weight of the crude ve nom. The molecular weights of both components were determined to be 2950 an d 2935 by mass spectrometry, which were fully coincidence with that of the known novel short-chain peptides BmP02 and BmP03, respectively [Romi-Lebrun R, Martin-Eauclaire M-F, Escoubas P, Wu FQ, Lebrun B, Hisada M, Nakajima T . Characterization of four toxins from Buthus martensi scorpion venom, whic h act on apamin-sensitive Ca2+-activated K+ channels. Eur J Biochem 1997;14 5:457-464]. In addition, the sequence of component F-2-7-4 was analyzed to be the same as that of BmP02. The components F-2-7-4 and F-2-7-5 purified i n this study were, thus, finally distinguished to be BmP02 and BmP03 from t he same venom. Using whole cell patch-clamp recording, it was found that Bm P02 diminished the current of transient outward K+ channel in adult rat ven tricular myocyte in a concentration-dependent manner. The inhibitory effect was reversible. Dynamic studies showed that the activation, inactivation a nd recovery processes of the transient outward K+ channel were not changed significantly after applying of BmP02. In addition, when BmP02 was applied to guinea pig ventricular myocyte, both delayed and inward rectified K+ cur rents showed no change compared with the control. The results suggest stron gly that BmP02 or -like peptides from scorpion venom may provide a useful p robe for the studying of transient outward K+ channel in rat ventricular my ocyte. (C) 2000 Elsevier Science B.V. All rights reserved.