Localization of a highly immunogenic region on the acetylcholine receptor α-subunit

Antibodies to synthetic peptides were employed in order to map domains on the α-subunit of the acetylcholine receptor to which several monoclonal antibodies are directed. Five peptides corresponding to residues 1-20, 126-143, 169-181, 330-340 and 351-368 of the receptor α-subunit were synthesized and antibodies against them were elicited. The anti-peptide antibodies were employed along with the monoclonal antibodies to identify fragments of S. aureus V8 protease digested-α-subunit in immunoblotting experiments. Our results demonstrate that a highly immunogenic region of the α-subunit is located on a carboxy-terminal 14 kDa portion of the α-subunit. This region also seems to undergo antigenic changes during muscle development. A monoclonal antibody directed against the cholinergic binding site of the acetylcholine receptor reacted with an 18 kDa segment of the α-subunit which bound α-bungarotoxin as well as antibodies directed against peptide 169-181.