Table II.

Open- and closed-time components for NMDA receptors comprised of WT or double-cysteine–substituted subunits

 N1/N2A N1(C,C)/N2A N1/N2A(C,C) DTT 
    N1/N2A N1(C,C)/N2A N1/N2A(C,C) 
n 
τO1 0.12 ± 0.01 0.25 ± 0.05 0.45 ± 0.09 3.0 ± 2.7 1.0 ± 0.7 4.7 ± 2.2 
aO1 6 ± 1.1 25 ± 4.7 42 ± 9.6 10 ± 5.7 7.2 ± 1.2 17 ± 8.2 
τO2 8.7 ± 0.9 1.6 ± 0.2 1.9 ± 0.13 26 ± 7 17 ± 5.6 34 ± 6.9 
aO2 94 ± 1.1 75 ± 4.7 59 ± 9.6 90 ± 5.7 93 ± 1.2 83 ± 8.2 
τ1 0.14 ± 0.01 0.25 ± 0.04 0.11 ± 0.01 0.12 ± 0.01 0.13 ± 0.01 0.10 ± 0.004 
a1 20 ± 1.5 13 ± 1.3 3.7 ± 0.3 31 ± 2.8 26 ± 3.5 31 ± 3.1 
τ2 1.0 ± 0.1 1.7 ± 0.6 2.1 ± 0.3 0.77 ± 0.16 0.8 ± 0.1 0.42 ± 0.02 
a2 24 ± 3.4 14 ± 1.6 8.7 ± 1.4 38 ± 6.9 44 ± 5.6 37 ± 3.3 
τ3 4.2 ± 0.4 38 ± 8.6 56 ± 9.0 3.8 ± 1.5 2.5 ± 0.4 1.1 ± 0.1 
a3 52 ± 3.4 53 ± 3.6 48 ± 4.4 29 ± 8.6 29 ± 8.5 30 ± 6.6 
τ4 27 ± 5.6 210 ± 45 150 ± 27 35 ± 15 20 ± 4.9 9.1 ± 0.7 
a4 3.6 ± 1.3 17 ± 3 33 ± 4.9 2.5 ± 1.0 1.2 ± 0.3 7.0 ± 5.1 
τ5 1,800 ± 370 1,800 ± 310 2,900 ± 360 1,100 ± 450 1,200 ± 680 250 ± 52 
a5 0.13 ± 0.03 3 ± 0.9 5.7 ± 0.9 0.5 ± 0.2 0.13 ± 0.03 0.13 ± 0.02 
 N1/N2A N1(C,C)/N2A N1/N2A(C,C) DTT 
    N1/N2A N1(C,C)/N2A N1/N2A(C,C) 
n 
τO1 0.12 ± 0.01 0.25 ± 0.05 0.45 ± 0.09 3.0 ± 2.7 1.0 ± 0.7 4.7 ± 2.2 
aO1 6 ± 1.1 25 ± 4.7 42 ± 9.6 10 ± 5.7 7.2 ± 1.2 17 ± 8.2 
τO2 8.7 ± 0.9 1.6 ± 0.2 1.9 ± 0.13 26 ± 7 17 ± 5.6 34 ± 6.9 
aO2 94 ± 1.1 75 ± 4.7 59 ± 9.6 90 ± 5.7 93 ± 1.2 83 ± 8.2 
τ1 0.14 ± 0.01 0.25 ± 0.04 0.11 ± 0.01 0.12 ± 0.01 0.13 ± 0.01 0.10 ± 0.004 
a1 20 ± 1.5 13 ± 1.3 3.7 ± 0.3 31 ± 2.8 26 ± 3.5 31 ± 3.1 
τ2 1.0 ± 0.1 1.7 ± 0.6 2.1 ± 0.3 0.77 ± 0.16 0.8 ± 0.1 0.42 ± 0.02 
a2 24 ± 3.4 14 ± 1.6 8.7 ± 1.4 38 ± 6.9 44 ± 5.6 37 ± 3.3 
τ3 4.2 ± 0.4 38 ± 8.6 56 ± 9.0 3.8 ± 1.5 2.5 ± 0.4 1.1 ± 0.1 
a3 52 ± 3.4 53 ± 3.6 48 ± 4.4 29 ± 8.6 29 ± 8.5 30 ± 6.6 
τ4 27 ± 5.6 210 ± 45 150 ± 27 35 ± 15 20 ± 4.9 9.1 ± 0.7 
a4 3.6 ± 1.3 17 ± 3 33 ± 4.9 2.5 ± 1.0 1.2 ± 0.3 7.0 ± 5.1 
τ5 1,800 ± 370 1,800 ± 310 2,900 ± 360 1,100 ± 450 1,200 ± 680 250 ± 52 
a5 0.13 ± 0.03 3 ± 0.9 5.7 ± 0.9 0.5 ± 0.2 0.13 ± 0.03 0.13 ± 0.02 

Mean values (±SEM) for the exponential time constants (τ) and their relative areas (a) of the open- and closed-interval distributions. Idealization and MIL fitting with the sequential NMDA receptor gating model comprising five closed- and two open-channel states was done in QuB (see Materials and methods). These data are shown as ratios relative to WT receptors in Fig. 6.

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