Tc30, A NOVEL TOXIN FROM THE AMAZONIAN SCORPION Tityus cambridgei THAT BLOCKS SHAKER B K ⁺ CHANNELS

BATISTA, C.V.F.(1), GÓMEZ-LAGUNAS, F.(1), ZAMUDIO, F.Z.(1), LUCAS, S.(2), POSSANI, L.D.(1)

(1)Department of Molecular Recognition and Structural Biology, Institute of Biotechnology, National Autonomous University of Mexico, Cuernavaca, México, (2)Instituto Butantan, São Paulo, Brazil.

The venom of scorpions constitutes a rich source of peptides toxic to a variety of organisms. In Brazil the scorpions of the family Buthidae, genus Tityus (T.) are medically important and several species have been studied, among which are: T. serrulatus, T. bahiensis, T. stigmurus. The venom of the scorpion T. cambridgei, has been less studied (Batista et al. Toxicon 40:557-562, 2002), although it contains a variety of peptides that affect Na⁺ and K⁺-channel function (Batista et al FEBS Lett. 486:117-120, 2000). In this communication we described the isolation, full sequence and electrophysiological studies of a novel toxin peptide (Tc30) from the venom of this Amazonian scorpion. This peptide was isolated by several steps of high performance liquid chromatography. It was sequenced by automatic Edman degradation and MS/MS fragmentation. Pure peptide was tested against Shaker B K⁺channels expressed in Sf9 cells. Tc 30 has 37 amino acid residues, with molecular mass of 3871.8 a.m.u., and contains three disulfide bridges. It is relatively potent inhibitor of Shaker B K⁺ channels with Kd value of 74 nM. Tc 30 has a lysine in the position 27 and a tyrosine at position 36, identical to those of Charybdotoxin. Comparison of the amino acid sequence of Tc30 with data bank data showed that it belong to the  Tytus II-9 subfamily and was given the number a-KTx4.4.

Acknowledgements: Supported in part by grants from DGAPA-UNAM (IN216900), CONACyT (31691-N and Z-005) and Howard Hughes Medical Institute (55000574), to LDP.

CORRESPONDENCE TO:

BATISTA, C.V.F., Department of Molecular Recognition and Structural Biology, Institute of Biotechnology, National Autonomous University of Mexico, Av. Universidad, 2001, Cuernavaca 62210 – Mexico, Email: fbatista@ibt.unam.mx