Upon acetylcholine binding, the AChR responds by an extensive change in conformation that affects all subunits and leads to opening of an ion-conducting channel across the plasma membrane. One of the alpha chains that assemble within the acetylcholine receptor, a pentamer of two alpha chains, a beta, a delta, and a gamma (in immature muscle) or epsilon (in mature muscle) chains. The muscle heteropentamer composed of alpha-1, beta-1, delta, epsilon subunits interacts with the alpha-conotoxin ImII. Belongs to the ligand-gated ion channel (TC 1.A.9) family. Acetylcholine receptor (TC 1.A.9.1) subfamily. Alpha-1/CHRNA1 sub-subfamily.