title: Noxiustoxin and leiurutoxin III, two homologous peptide toxins with binding properties to synaptosomal membrane K+ channels.
abstract: Noxiustoxin (NTX), a short-chain peptide toxin from the scorpion C. noxius, binds to a single class of non-interacting binding sites in brain synaptosomal membranes with a KD = 160-300 nM and a Bmax = 2.2 pmols.mg-1 protein. The K+ channel blocking agents tetraethylammonium, 4-aminopyridine and Charybdotoxin partially inhibit the binding of [125I]NTX, while a variety of toxins targeted against Ca2+ and Na+ channels have no effect, suggesting that NTX interacts with a bona fide K+ channel protein. NTX totally displaces the binding of [125I]Leiurutoxin III, a novel peptide from L. quinquestriatus venom with N-terminal amino acid sequence homologous to that of NTX. These results suggest that both toxins bind to a common receptor site and are promising tools to dissect the molecular mechanisms of channel-toxin interaction.
mesh_terms: D015761:4-Aminopyridine / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D018999:Charybdotoxin; D036341:Intercellular Signaling Peptides and Proteins; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009498:Neurotoxins / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D012604:Scorpion Venoms / Q000378:metabolism* / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid; D013570:Synaptic Membranes / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; D009498:Neurotoxins; D010455:Peptides; D015221:Potassium Channels; D012604:Scorpion Venoms; D013757:Tetraethylammonium Compounds; C077585:leiurutoxin III; D018999:Charybdotoxin; D019789:Tetraethylammonium; C052567:noxiustoxin; D015761:4-Aminopyridine