Figure 6.
The GluR2 L483Y mutant strongly reduces trapping. A, In the presence of 1 mm DTT, the L483Y-S729C double mutant does not desensitize in response to a 25 ms application of 10 mm glutamate. B, In response to a 500 ms application of glutamate the extent (9 ± 1%) and rate of desensitization (kdes = 4.5 ± 1.5 s–1, n = 3 patches) for the L483Y-S729C double mutant are similar those previously found for the L483Y single mutant (data from Sun et al., 2002). C, At rest the L483Y-S729C double mutant shows no detectable trapping following an 80 s exposure to 10 μm CuPhen, although as shown below with much longer applications weak trapping was observed. D, In contrast the L483Y-S729C double mutant can be efficiently trapped by application of 300 μm glutamate at a rate of 0.13 ± 0.03 s–1, n = 5 patches, estimated from the fit of a single exponential (white dashed line). E, Rate and extent of trapping by glutamate in oxidizing conditions was concentration dependent. The dashed line shows the faster trapping of the single S729C mutant in glutamate. We detected trapping when the receptor was exposed to oxidizing conditions for long intervals (>100 s) in the absence of any ligand, and this was apparently abolished, at least on the timescale of our measurements, when domain 2 was restrained by binding of CNQX (30 μm).