title: OcyKTx2, a new K⁺-channel toxin characterized from the venom of the scorpion Opisthacanthus cayaporum.
abstract: Opisthacanthus cayaporum belongs to the Liochelidae family, and the scorpions from this genus occur in southern Africa, Central America and South America and, therefore, can be considered a true Gondwana heritage. In this communication, the isolation, primary structure characterization, and K⁺-channel blocking activity of new peptide from this scorpion venom are reported. OcyKTx2 is a 34 amino acid long peptide with four disulfide bridges and molecular mass of 3807 Da. Electrophysiological assays conducted with pure OcyKTx2 showed that this toxin reversibly blocks Shaker B K⁺-channels with a Kd of 82 nM, and presents an even better affinity toward hKv1.3, blocking it with a Kd of ∼18 nM. OcyKTx2 shares high sequence identity with peptides belonging to subfamily 6 of α-KTxs that clustered very closely in the phylogenetic tree included here. Sequence comparison, chain length and number of disulfide bridges analysis classify OcyKTx2 into subfamily 6 of the α-KTx scorpion toxins (systematic name, α-KTx6.17).
authors.affiliation: Department of Physiological Sciences, Institute of Biological Sciences, University of Brasilia, Brasilia, 70910-900 DF, Brazil. efschwa@unb.br
authors.forename: Elisabeth F
authors.initials: EF
authors.lastname: Schwartz
authors.forename: Adam
authors.initials: A
authors.lastname: Bartok
authors.forename: Carlos Alberto
authors.initials: CA
authors.lastname: Schwartz
authors.forename: Ferenc
authors.initials: F
authors.lastname: Papp
authors.forename: Froylan
authors.initials: F
authors.lastname: Gómez-Lagunas
authors.forename: Gyorgy
authors.initials: G
authors.lastname: Panyi
authors.forename: Lourival D
authors.initials: LD
authors.lastname: Possani
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D051664:Kv1.3 Potassium Channel / Q000037:antagonists & inhibitors*; D010455:Peptides / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D026902:Potassium Channel Blockers / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D011485:Protein Binding; D012604:Scorpion Venoms / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D012605:Scorpions / Q000378:metabolism; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D051637:Shaker Superfamily of Potassium Channels / Q000037:antagonists & inhibitors*
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; C587490:KTx2 protein, Opisthacanthus cayaporum; D051664:Kv1.3 Potassium Channel; D010455:Peptides; D026902:Potassium Channel Blockers; D012604:Scorpion Venoms; C076413:Shaker B potassium channel polypeptide; D051637:Shaker Superfamily of Potassium Channels
keywords: OcyKTx2; Opisthacanthus cayaporum; Scorpion toxin; Shaker B K(+)-channel; hKv1.3; lymphocyte