Figure 9

Effects of mutations within nucleotide-binding domain of SUR1 on channel activation by NO. (A) Representative traces of currents via SUR1-C717S/Kir6.2 channels in inside-out patches at -60 mV holding potential. Bath application of ATP (1 mM) inhibited SUR1-C717S/Kir6.2 channels. Arrows indicate closed channel state. (B) Concentration-response relationship curves between [ATP]i and relative NPo values for wild-type SUR1/Kir6.2 or SUR1-C717S/Kir6.2 channels. The relative channel activities were calculated by dividing the channel activity in the presence of various [ATP]i with the activity in the absence of ATP. Each point represents measurements from 7 patches (mean ± SD). (C) Representative current traces of SUR1-C717S/Kir6.2 channel currents in inside-out patches at -60 mV holding potential. In the presence of 1 mM [ATP]i, bath application of SNAP (1 mM) activated SUR1-C717S/Kir6.2 channel, but less than wild-type SUR1/Kir6.2 channels. Activation of these currents was suppressed by the subsequent application of a thiol-reducing agent, DTT (5 mM). Arrows indicate closed channel state. (D) Summary of ATP-sensitivity and SNAP effects on relative NPo values of wild-type (control) and mutated SUR1/Kir6.2 currents. The relative channel activities were calculated by dividing the channel activity in the presence or absence (1 mM [ATP]i only) of SNAP (100 μM) with the activity in the absence of ATP. Each horizontal bar represents measurements from 7–8 patches (mean ± SD).