Figure 1.

Redox sensitivity of wild-type GluR2 and the G725C and S729C mutants. A, Crystal structure of the GluR2 ligand binding dimer glutamate complex (PDB 1FTJ) in which domains 1 and 2 in each subunit are colored blue and pink, respectively; orange spheres separated by 16 Å indicate the wide separation of the CA atoms of the G725C mutant in the glutamate bound active state. B, Diagram representation of the ligand binding domain and ion channel in the glutamate bound open state; the introduced cysteine residues are shown as orange bars. C, Activation and desensitization of wild-type GluR2 is not affected by redox potential; the colored lines show single exponential fits to the decay of the response to glutamate; the rise time and rate of desensitization for glutamate responses in control conditions, k_des 129 s⁻¹ (blue), was indistinguishable from that in 10 μm CuPhen, k_des 116 s⁻¹ (red), or 1 mm DTT, k_des 131 s⁻¹ (cyan). D, Activation and desensitization of the G725C mutant in reducing conditions, k_des 280 s⁻¹ (blue) had similar kinetics to wild-type, but when the patch was bathed in oxidizing conditions a rapid but reversible loss of current was observed; upon recovery in DTT, k_des 250 s⁻¹ (cyan), responses were generally smaller than control. E, Similar redox sensitivity was observed for the S729C mutant, control k_des 298 s⁻¹ (blue), but full recovery occurred on return to DTT, k_des 304 s⁻¹ (cyan). F, Bar plot of desensitization rates in response to 10 mm glutamate in reducing conditions (1 mm DTT); values are mean ± SEM of 5 – 9 observations per construct.