Isolation and characterization of a monoclonal antibody against the saxitoxin-binding component from the electric organ of the eel Electrophorus electricus.

A monoclonal hybridoma cell line secreting antibody against the saxitoxin-binding component from the eel Electrophorus electricus has been isolated. The specificity of this monoclonal antibody was established by (i) its ability to immunoprecipitate bound [3H]saxitoxin from a detergent extract of electroplax membranes in a dose-dependent manner, (ii) the inability of unrelated monoclonal antibodies to immunoprecipitate the toxin-binding activity in a similar assay, and (iii) the ability of excess unlabeled tetrodotoxin to displace [3H]saxitoxin from the immunoprecipitated component. The antibody is of the subclass IgG1 and binds specifically to a polypeptide component of Mr approximately 250,000 on NaDodSO4/polyacrylamide gels. The antigenic determinant is associated with the same polypeptide component throughout the purification procedure, indicating that this component is not a result of artifactual aggregation or degradation during isolation. We conclude that the 250,000-dalton polypeptide is part of the saxitoxin binding/sodium channel protein in the native electroplax membrane.