Cys-loop family

All the cys-loop family of ligand-gated ion channels is responsible for the rapid neurotrans-mission. They are pentamers. Each of the subunit has extracellular N and C terminals and four transmembrane a-helical segments (M1–M4). All members having subunits are responsible for the agonist of binding. The disulfide bond between two cysteine residues at the N-terminus forms a loop needed for binding (and this is the reason for the “cys-loop” description). The M2 domains of α subunits form the ion pore. There is modest amino acid homology between the subunits within and across the cys-loop receptors.