A K⁺ channel blocking peptide from the Cuban scorpion Rhopalurus garridoi.

A proteomic analysis of the venom obtained from the Cuban scorpion Rhopalurus garridoi was performed. Venom was obtained by electrical stimulation, separated by high performance liquid chromatography, and the molecular masses of their 50 protein components were identified by mass spectrometry. A peptide of 3940 Da molecular mass was obtained in pure form and its primary structure determined. It contains 37 amino acid residues, including three disulfide bridges. Electrophysiological experiments showed that this peptide is capable of blocking reversibly K(+)-channels hKv1.1 with a Kd close to 1 μM, but is not effective against hKv1.4, hERG1 and EAG currents, at the same concentration. This is the first protein component ever isolated from this species of scorpion and was assigned the systematic number α-KTx 2.14.