Abstract :
[en] Sea anemone venoms have become a rich source of peptide toxins which
are invaluable tools for studying the structure and functions of ion channels.
In this work, BcsTx3, a toxin found in the venom of a Bunodosoma
caissarum (population captured at the Saint Peter and Saint Paul
Archipelago, Brazil) was purified and biochemically and pharmacologically
characterized. The pharmacological effects were studied on 12 different
subtypes of voltage-gated potassium channels (KV1.1–KV1.6; KV2.1;
KV3.1; KV4.2; KV4.3; hERG and Shaker IR) and three cloned voltagegated
sodium channel isoforms (NaV1.2, NaV1.4 and BgNaV1.1) expressed
in Xenopus laevis oocytes. BcsTx3 shows a high affinity for Drosophila
Shaker IR channels over rKv1.2, hKv1.3 and rKv1.6, and is not active on
NaV channels. Biochemical characterization reveals that BcsTx3 is a 50
amino acid peptide crosslinked by four disulfide bridges, and sequence
comparison allowed BcsTx3 to be classified as a novel type of sea anemone
toxin acting on KV channels. Moreover, putative toxins homologous to
BcsTx3 from two additional actiniarian species suggest an ancient origin of
this newly discovered toxin family.
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