Fig. 3: The four-subunit model behaves qualitatively identical to the one-subunit version.

a Transitions in the four-subunit model diagram, showing only the first ligand binding event. b Deterministic time courses with increasing ligand concentrations. Plot shows receptor occupancy (normalized sum of all species with bound L-glutamate) and current (normalized species with at least one subunit in open configuration), drawn with negative numbers vs. time. Darker corresponds to higher ligand (L-glutamate) concentration. c Inset shows the design of the simulated pre-incubation experiment. Red: peak current vs L-glutamate concentration during pre-incubation. Blue: peak current obtained when stimulated with 10⁴ µM L-glutamate after being preincubated with the indicated L-glutamate concentrations. d Plot shows the dose–response curves for peak current (solid), steady-state ligand binding (dotted line), and ligand binding at different times after the addition of L-glutamate (coded using a colormap). Colored circles highlight binding at the time of peak current at the indicated L-glutamate concentrations. The values used for the dose–response curves are from (b). Ligand concentrations that elicit 50% of maximum response are marked with solid black lines for the steady-state ligand binding and peak current dose–response curves.