title: Binding of anti-acetylcholine receptor antibodies inhibits the acetylcholine receptor mediated cation flux.
abstract: A fast kinetics, spectroscopic technique has been applied to the study of the transient cation flux associated to the binding of cholinergic agonist to native acetylcholine receptor (AcChR)-rich membrane vesicles in presence of anti-AcChR antibodies. The technique is based on the collisional quenching of an intravesicularly trapped fluorophore by externally added T1+ which substitutes for physiologically occurring cations. Presence of polyclonal Fab fragments from goat anti-AcChR antibodies bound to the membrane AcChR promotes a 80-90% inhibition on the observed rate constants of T1+ influx. The observed inhibition process appears to follow a non-competitive pattern between antibody and cholinergic ligand binding, suggesting that in the AcChR protein the antigenic sites responsible for ion translocation may be other than those involved in ligand binding.
mesh_terms: D000818:Animals; D001323:Autoantibodies / Q000502:physiology*; D002412:Cations; D002463:Cell Membrane Permeability; D004557:Electric Organ / Q000032:analysis*; D000939:Epitopes; D005456:Fluorescent Dyes; D007140:Immunoglobulin Fab Fragments; D011721:Pyrenes / Q000378:metabolism; D011950:Receptors, Cholinergic / Q000276:immunology* / Q000378:metabolism; D013793:Thallium / Q000378:metabolism; D014101:Torpedo / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D002412:Cations; D000939:Epitopes; D005456:Fluorescent Dyes; D007140:Immunoglobulin Fab Fragments; D011721:Pyrenes; D011950:Receptors, Cholinergic; D013793:Thallium; C041343:1,3,6,8-pyrene tetrasulfonate