Monoclonal antibodies specific to the beta and gamma subunits of the Torpedo acetylcholine receptor inhibit single-channel activity.

The functional role of individual ACh receptor subunits in the mechanism of the nicotinic ACh receptor channel was examined using subunit-specific monoclonal antibodies (mAbs) as probes. Single-channel recordings from the Torpedo californica purified ACh receptor reconstituted in planar lipid bilayers were used as the assay to evaluate the influence of distinct mAbs on the ion conduction and gating characteristics of the ACh receptor channel. The mAbs that bind to the main immunogenic region on an extracellular domain of the alpha subunits do not perturb the open-channel conductance or lifetimes. A mAb that binds to extracellular domains of alpha and beta subunits and two mAbs that bind to the cytoplasmic surface of the beta and gamma subunits inhibit single-channel activity. Thus, mAbs with primary specificity for beta and gamma subunits affect channel gating. This approach may specify the functional roles of distinct structural domains in the ACh receptor molecule.