Non-alpha subunit of nicotinic acetylcholine receptor (nAChR). Involved in nAChR sensitivity to nicotine. Interacts with unc-29. Component of nicotinic acetylcholine receptor composed of 2 non-alpha subunits lev-1 and unc-29, and 3 alpha subunits unc-38, unc-63 and lev-8. Co-localizes with unc-29 and unc-38 at nerve cord synapses. RNAi-mediated knockdown causes a resistance to nicotine-mediated paralysis. Belongs to the ligand-gated ion channel (TC 1.A.9) family. Acetylcholine receptor (TC 1.A.9.1) subfamily.