The inhibitory glycine receptor is characterized by a pentameric arrangement of subunits with four predicted transmembrane segments (M1-M4) each. Here, we have mutagenized arginine residues located at both termini of the alpha 1 subunit segment, M2, which lines the receptor's anion channel. No glycine-gated channel formation could be detected in the plasma membrane of expressing cells for any of the mutants. In addition, mutating the arginine at the cytoplasmic terminus of M2 (R219) generated proteins which were only core-glycosylated, retained within intracellular compartments, and aggregated to high molecular weight complexes. Thus, residue R219, which corresponds to an arginine/lysine conserved in other ligand-gated ion channel polypeptides, is essential for correct biogenesis of the receptor.