title: Binding characteristics of BmK I, an alpha-like scorpion neurotoxic polypeptide, on cockroach nerve cord synaptosomes.
abstract: In this study, the binding characteristics of BmK I, an alpha-like neurotoxic polypeptide purified from the venom of the Chinese scorpion Buthus martensi Karsch, were investigated on rat brain and cockroach nerve cord synaptosomes. The results showed that BmK I can bind to a single class of noninteracting binding sites on cockroach nerve cord synaptosomes with medium affinity (Kd = 16.5 +/ - 4.4 nM) and low binding capacity (Bmax = 1.05 +/- 0.23 pmol/mg protein), but lacks specific binding on rat brain synaptosomes. BmK AS, BmK AS-1 (two novel sodium channel-blocking ligands), BmK IT (an excitatory insect-selective toxin) and BmK IT2 (a depressant insect-selective toxin) from the same venom were found to be capable of depressing BmK I binding in cockroach nerve cord synaptosomes, which might be attributed to either allosteric modulation of voltage-gated Na+ channels by these toxic polypeptides or partial overlapping between the receptor binding sites of BmK I and these toxins. This thus supported the notion that alpha-like scorpion neurotoxic polypeptides bind to a distinct receptor site on sodium channels, which might be similar to the binding receptor site of alpha-type insect toxins, and also related to those of BmK AS type and insect-selective scorpion toxins on insect sodium channels.
authors.affiliation: Shanghai Institute of Physiology, Chinese Academy of Sciences.
authors.forename: Y J
authors.initials: YJ
authors.lastname: Li
authors.forename: Y H
authors.initials: YH
authors.lastname: Ji
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000166:cytology / Q000378:metabolism; D003058:Cockroaches / Q000166:cytology / Q000378:metabolism*; D019476:Insect Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D007457:Iodine Radioisotopes; D008969:Molecular Sequence Data; D009154:Mutation; D009420:Nervous System / Q000166:cytology / Q000378:metabolism*; D009498:Neurotoxins / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D012604:Scorpion Venoms / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D026941:Sodium Channel Blockers; D015222:Sodium Channels / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism*
chemical_list: C119407:BmK AS polypeptide; D019476:Insect Proteins; D007457:Iodine Radioisotopes; C119408:KAS-1 toxin, Buthus martensi; D009498:Neurotoxins; D010455:Peptides; D012604:Scorpion Venoms; D026941:Sodium Channel Blockers; D015222:Sodium Channels; C105338:makatoxin I