FIGURE 5.
The N160D mutation induces inward rectification on the WT- but not the G156R- or G156K-Kir6.2 background. COSm6 cells were transfected with cDNAs of SUR1 and one of the following Kir6.2s: WT, N160D, G156R/N160D, or G156K/N160D. Inside-out patches were subjected to a voltage-ramp protocol (membrane potential 100 to −100 mV) in control K-INT solution or K-INT solution containing 20 μm spermine. The pipette solution was K-INT. Representative experiments for each channel type are shown. Currents were normalized (Irel) to that seen at −100 mV. Although currents from N160D channels were completely blocked by spermine at positive membrane potentials, little block was observed for WT, G156R/N160D, or G156K/N160D channels. Similar results were obtained from four experiments.