Antibodies to a synthetic peptide corresponding to residues 346–359 of the Torpedo acetylcholine receptor (AChR) γ subunit, were employed to compare the adult and embryonic receptor. This peptide contains a consensus phosphorylation site for cAMP-dependent protein kinase (PKA). The anti-peptide antibodies discriminated between adult and embryonic AChRs, and reacted preferentially with the adult γ form. These observed immunological differences did not seem to stem from different phosphorylation states. Our results suggest that the embryonic Torpedo AChR may have a γ-like subunit that differs from the known adult form of this subunit, at least in the specific region that contains the phosphorylation site for PKA.
