Two y2L subunit domains confer low Zn sensitivity to ternary GABAA receptors

major inhibitory neurotransmitter receptor in the mammalian central nervous system. Functional mammalian GABARs are thought to be pentameric combinations of homologous subunits drawn from seven different families with multiple subtypes: a(1–6), b(1–3), y(1–3), d, e, π and  (Macdonald & Olsen, 1994; Davies et al. 1997; Hedblom & Kirkness, 1997; Bonnert et al. 1999). Like other members of the ligand-gated ion channel gene superfamily, GABAR subunits have a putative membrane topology consisting of a large N-terminus, four membranespanning segments (M1–M4), one extracellular and two intracellular loops connecting the membrane-spanning segments (M1–M2, M2–M3, M3–M4), and an extracellular C-terminus. It has been suggested that neuronal GABARs are predominantly ternary aby and abd combinations (Angelotti et al. 1993; McKernan & Whiting, 1996).