Stoichiometry of a recombinant GABAA receptor deduced from mutation-induced rectification

Abstract

Ligand-gated ion channels generally display a heterooligomeric subunit structure. The present report describes an electrophysiological method that provides criteria indicating the subunit stoichiometry of a recombinant GABAA receptor composed of α3, β2 and γ2 subunits. Our results exclude the stoichiometries 3α1β1γ, 1α3β1γ, 1α1β3γ and suggest that the possible subunit stoichiometries for this receptor are 2α1β2γ, 2α2β1γ or 1α2β2γ, of which the α subunit composition 2α1β2γ may be favoured. The method is based on the quantification of the outward rectification of the GABA-evoked current induced by point mutation of charged amino acids located near the ion channel pore.