Dose–response relationships for selected glutamate scan mutants. (A) GABA-gated currents at a range of agonist concentrations in oocytes expressing the indicated mutants are shown. (B) Maximum current amplitudes were plotted as a function of GABA concentration and fitted with the Hill equation (Eq. 1 in Materials and methods). Parameters from these fits are provided in Table I. In general, the mutations had a modest effect on agonist sensitivity.