PhcrTx2, a new crab-paralyzing peptide toxin from the sea anemone phymanthus crucifer

Sea anemones produce proteinaceous toxins for predation and defense, including peptide toxins that act on a large variety of ion channels of pharmacological and biomedical interest. Phymanthus crucifer is commonly found in the Caribbean Sea; however, the chemical structure and biological activity of its toxins remain unknown, with the exception of PhcrTx1, an acid-sensing ion channel (ASIC) inhibitor. Therefore, in the present work, we focused on the isolation and characterization of new P. crucifer toxins by chromatographic fractionation, followed by a toxicity screening on crabs, an evaluation of ion channels, and sequence analysis. Five groups of toxic chromatographic fractions were found, and a new paralyzing toxin was purified and named PhcrTx2. The toxin inhibited glutamate-gated currents in snail neurons (maximum inhibition of 35%, IC50 4.7 mu M), and displayed little or no influence on voltage-sensitive sodium/potassium channels in snail and rat dorsal root ganglion (DRG) neurons, nor on a variety of cloned voltage-gated ion channels. The toxin sequence was fully elucidated by Edman degradation. PhcrTx2 is a new -defensin-fold peptide that shares a sequence similarity to type 3 potassium channels toxins. However, its low activity on the evaluated ion channels suggests that its molecular target remains unknown. PhcrTx2 is the first known paralyzing toxin in the family Phymanthidae.
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sea anemone;  neutoxin; glutamate receptor;  defensin-like fold;  ion channels;  Phymanthus crucifer

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Rodriguez AA, Garateix A, Salceda E, Peigneur S, Zaharenko AJ, Pons T, et al. PhcrTx2, a new crab-paralyzing peptide toxin from the sea anemone phymanthus crucifer. Toxins. 2018 Feb;10(2):72. doi:10.3390/toxins10020072.
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