Topological mapping of acetylcholine receptor: evidence for a model with five transmembrane segments and a cytoplasmic COOH-terminal peptide.

Open Access
Publisher Website
Google Scholar
Abstract
Antibodies were raised against 2 synthetic peptides whose sequences correspond, respectively, to the COOH-terminal end (residues 501-516) of the protein encoded by the gene for the .delta. chain and to a proposed cytoplasmic region (residues 350-358) of the .beta. chain of the acetylcholine receptor from Torpedo californica. Binding of the COOH-terminal antibody to the acetylcholine receptor in intact, receptor-rich vesicles was tested by radioimmunoassay and by precipitation with immobilized protein A. In both cases, binding was detected only after treatment of the vesicles with detergent, suggesting that the segment of the receptor that is recognized by this antibody is on the cytoplasmic side of the membrane. EM of tissue from Torpedo electric organ labeled with colloidal gold-conjugated second antibodies established that both anti-receptor antibodies bind to the cytoplasmic surface of the postsynaptic membrane. The COOH-terminal segment of the .delta. chain as well as residues 350-358 of the .beta. chain are on the cytoplasmic surface. They strongly support a model in which each of the receptor subunits crosses the membrane 5 times and in which one transmembrane segment of each chain contributes to the formation of a central ion channel.

This publication has 35 references indexed in Scilit: