BmK AS: new scorpion neurotoxin binds to distinct receptor sites of mammal and insect voltage-gated sodium channels.
This study was undertaken to assess the binding properties of BmK AS on both mammal and insect excitable cell membranes. It was found that BmK AS bound specifically to a single class of non-interacting binding sites on both rat brain and cockroach nerve cord synaptosomes with high affinity (K(d) = 1.49 +/- 0.14 and 0.79 +/- 0.29 nM) and low capacity (B(max) = 1.39 +/- 0.09 and 6.60 +/- 1.25 pmol/mg protein), respectively. Binding kinetics showed that BmK AS could bind and reach equilibrium quickly, and dissociate partially from its binding sites on both kinds of synaptosomes. The binding of BmK AS was independent of membrane potential. Veratridine could not modify the binding of BmK AS. The competitive binding assay showed that specific binding of (125)I-BmK AS could be significantly inhibited by native BmK AS, BmK AS-1, BmK IT2 and BmK IT on both synaptosomes. Unexpectedly, only about 20-30% binding of BmK AS on mammal synaptosomes was inhibited by BmK I at 10(-5)-10(-9) M, but not on insect synaptosomes. It thus suggests that BmK AS type neurotoxins might bind to a distinct receptor site of sodium channels on mammal and insect excitable cell membranes with a manner similar to beta-scorpion toxins.
Li
Y J
YJ
Shanghai Institute of Physiology, Chinese Academy of Sciences, Shanghai, People's Republic of China.
Liu
Y
Y
Ji
Y H
YH
D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D001923:Brain Chemistry / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009498:Neurotoxins / Q000494:pharmacology; D010455:Peptides / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D010526:Periplaneta; D051381:Rats; D017208:Rats, Wistar; D012604:Scorpion Venoms / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D015222:Sodium Channels / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D013045:Species Specificity; D013574:Synaptosomes / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D014701:Veratridine / Q000494:pharmacology
C119407:BmK AS polypeptide; C119408:KAS-1 toxin, Buthus martensi; D009498:Neurotoxins; D010455:Peptides; D012604:Scorpion Venoms; D015222:Sodium Channels; C029574:scorpion toxin receptor; D014701:Veratridine