Gating modifier toxins reveal a conserved structural motif in voltage-gated Ca2+ and K+ channels.
Protein toxins from venomous animals exhibit remarkably specific and selective interactions with a wide variety of ion channels. Hanatoxin and grammotoxin are two related protein toxins found in the venom of the Chilean Rose Tarantula, Phrixotrichus spatulata. Hanatoxin inhibits voltage-gated K+ channels and grammotoxin inhibits voltage-gated Ca2+ channels. Both toxins inhibit their respective channels by interfering with normal operation of the voltage-dependent gating mechanism. The sequence homology of hanatoxin and grammotoxin, as well as their similar mechanism of action, raises the possibility that they interact with the same region of voltage-gated Ca2+ and K+ channels. Here, we show that each toxin can interact with both voltage-gated Ca2+ and K+ channels and modify channel gating. Moreover, mutagenesis of voltage-gated K+ channels suggests that hanatoxin and grammotoxin recognize the same structural motif. We propose that these toxins recognize a voltage-sensing domain or module present in voltage-gated ion channels and that this domain has a highly conserved three-dimensional structure.
Li-Smerin
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Y
Molecular Physiology and Biophysics Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA.
Swartz
K J
KJ
D000595:Amino Acid Sequence; D000818:Animals; D015220:Calcium Channels / Q000737:chemistry / Q000187:drug effects*; D015640:Ion Channel Gating; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology*; D010456:Peptides, Cyclic / Q000737:chemistry / Q000494:pharmacology*; D015221:Potassium Channels / Q000737:chemistry / Q000187:drug effects*; D017386:Sequence Homology, Amino Acid; D014982:Xenopus laevis
D015220:Calcium Channels; D010455:Peptides; D010456:Peptides, Cyclic; D015221:Potassium Channels; C096469:hanatoxin; C082807:omega-grammotoxin SIA