Binding to saxitoxin to electrically excitable neuroblastoma cells.
Saxitoxin inhibits the action potential Na+ ionophore of electrically excitable neuroblastoma cells with a KI of 3.7 nM. Binding experiments detect a single class of saturable binding sites with KD = 3.9 nM and a binding capacity of 156 fmol/mg of cell protein (78 sites per micrometer2 of cell surface). Saturable binding is completely inhibited by tetrodotoxin but is unaffected by scorpion toxin or batrachotoxin. No saturable binding is observed in cultures of clone N103, a variant neuroblastoma clone lacking the action potential Na+ response. Thus, saxitoxin binds specifically to the action potential Na+ ionophore in neuroblastoma cells. Comparison of saxitoxin and scorpion toxin binding reveals that there are three saxitoxin receptor sites for each scorpion toxin receptors site. The implications of this stoichiometry are considered.
D000200:Action Potentials / Q000187:drug effects; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D007476:Ionophores / Q000037:antagonists & inhibitors; D009447:Neuroblastoma / Q000378:metabolism; D009474:Neurons / Q000378:metabolism*; D011955:Receptors, Drug / Q000378:metabolism*; D012530:Saxitoxin / Q000378:metabolism* / Q000494:pharmacology; D012604:Scorpion Venoms / Q000378:metabolism; D012964:Sodium / Q000378:metabolism
D007476:Ionophores; D011955:Receptors, Drug; D012604:Scorpion Venoms; D012530:Saxitoxin; D012964:Sodium
J Mol Biol. 1965 May;12:88-118
14343300
J Gen Physiol. 1964 May;47:965-74
14155438
J Physiol. 1952 Aug;117(4):500-44
12991237
J Physiol. 1976 Oct;261(2):477-94
978583
Nature. 1977 Mar 31;266(5601):465-8
558521
J Biol Chem. 1976 Sep 25;251(18):5528-36
965375
Philos Trans R Soc Lond B Biol Sci. 1975 Jun 10;270(908):349-52
238233
Proc Natl Acad Sci U S A. 1972 Dec;69(12):3634-7
4509325
Proc Natl Acad Sci U S A. 1974 Oct;71(10):3936-40
4530274
Proc Natl Acad Sci U S A. 1976 Aug;73(8):2682-6
1066680
Proc Natl Acad Sci U S A. 1975 May;72(5):1782-6
1057169
Biochem Biophys Res Commun. 1975 May 5;64(1):115-21
1147916
J Biol Chem. 1975 Jun 10;250(11):4053-9
1168643
J Cell Physiol. 1971 Jun;77(3):337-52
5092540
J Gen Physiol. 1968 Feb;51(2):199-219
5641635