Interrelationship of concanavalin-A-binding and antigenic sites on the acetylcholine receptor from Torpedo marmorata

A preparation of purified 125I-labelled acetylcholine receptor was shown to bind to concanavalin A and to be totally bound by rabbit antiserum to Torpedo acetylcholine receptor. Pre-incubation of the receptor with F(ab')2 and Fab fragments from antibodies against Torpedo acetylcholine receptor, or with corresponding fragments from control immunoglobulin G showed that subsequent binding of the receptor to concanavalin A was specifically inhibited to a maximum of approximately 25% by the immune fragments. Treatment of acetylcholine receptor with periodate or with glycosidases apparently destroyed or removed carbohydrate residues without affecting the antigenicity of the receptor as assessed by radioimmunoassay. These results suggest that although there is a steric interrelatonship between the antigenic and concanavalin-A-binding sites of the receptor the latter sites do not contain its major antigenic determinants.