title: Two novel toxins from the Amazonian scorpion Tityus cambridgei that block Kv1.3 and Shaker B K(+)-channels with distinctly different affinities.
abstract: Two novel toxic peptides (Tc30 and Tc32) were isolated and characterized from the venom of the Brazilian scorpion Tityus cambridgei. The first have 37 and the second 35 amino acid residues, with molecular masses of 3,871.8 and 3,521.5, respectively. Both contain three disulfide bridges but share only 27% identity. They are relatively potent inhibitors of K(+)-currents in human T lymphocytes with K(d) values of 10 nM for Tc32 and 16 nM for Tc30, but they are less potent or quite poor blockers of Shaker B K(+)-channels, with respective K(d) values of 74 nM and 4.7 microM. Tc30 has a lysine in position 27 and a tyrosine at position 36 identical to those of charybdotoxin. These two positions conform the dyad considered essential for activity. On the contrary, Tc32 has a serine in the position equivalent to lysine 27 of charybdotoxin and does not contain any aromatic amino acid. Due to its unique primary sequence and to its distinctive preference for K(+)-channels of T lymphocytes, it was classified as the first example of a new subfamily of K(+)-channel-specific peptides (alpha-KT x 18.1). Tc30 is a member of the Tityus toxin II-9 subfamily and was given the number alpha-KT x 4.4.
authors.affiliation: Department of Molecular Recognition and Structural Biology, Institute of Biotechnology, National Autonomous University of Mexico, Colonia Chamilpa Avenida Universidad, 2001 Cuernavaca 62210, Mexico.
authors.forename: Cesar V F
authors.initials: CV
authors.lastname: Batista
authors.forename: Froylan
authors.initials: F
authors.lastname: Gómez-Lagunas
authors.forename: Ricardo C
authors.initials: RC
authors.lastname: Rodríguez de la Vega
authors.forename: Péter
authors.initials: P
authors.lastname: Hajdu
authors.forename: György
authors.initials: G
authors.lastname: Panyi
authors.forename: Rezsõ
authors.initials: R
authors.lastname: Gáspár
authors.forename: Lourival D
authors.initials: LD
authors.lastname: Possani
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001938:Brazil; D006801:Humans; D051664:Kv1.3 Potassium Channel; D008969:Molecular Sequence Data; D010455:Peptides / Q000187:drug effects* / Q000235:genetics; D026902:Potassium Channel Blockers / Q000737:chemistry / Q000302:isolation & purification / Q000633:toxicity*; D015221:Potassium Channels / Q000187:drug effects* / Q000235:genetics; D024642:Potassium Channels, Voltage-Gated; D012604:Scorpion Venoms / Q000737:chemistry / Q000302:isolation & purification / Q000633:toxicity*; D012605:Scorpions; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D051637:Shaker Superfamily of Potassium Channels; D018411:Spodoptera; D014162:Transfection
chemical_list: C496973:KCNA3 protein, human; D051664:Kv1.3 Potassium Channel; D010455:Peptides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012604:Scorpion Venoms; C076413:Shaker B potassium channel polypeptide; D051637:Shaker Superfamily of Potassium Channels