Table 1.
Relative permeabilities for Na+ and K+ ions of mutant Kir3.2 channels
| Mutation(s) | ΔE | PNa/PK | n | After TPNQ subtraction |
||
|---|---|---|---|---|---|---|
| ΔE | PNa/PK | n | ||||
| S177T | −74.6 ± 1.9 | 0.06 ± 0.004 | 10 | −131.4 ± 3.6 | 0.006 ± 0.0009 | 4 |
| S177W | −15.3 ± 0.8 | 0.56 ± 0.02 | 23 | −16.3 ± 2.3 | 0.54 ± 0.04 | 4 |
| S177W-N184Q | −20.3 ± 1.4 | 0.47 ± 0.02 | 18 | — | — | — |
| S177W-N184D | −78 ± 7.1 | 0.06 ± 0.01 | 6 | −126.4 ± 4.1 | 0.008 ± 0.001 | 8 |
| S177W-N184E | −82.1 ± 3.1 | 0.04 ± 0.006 | 10 | −95.8 ± 7.5 | 0.03 ± 0.006 | 3 |
| S177W-N184R | −14.8 ± 0.8 | 0.56 ± 0.02 | 7 | — | — | — |
| S177W-N184K | −14.1 ± 0.9 | 0.58 ± 0.02 | 9 | — | — | — |
| S177W-N184S | −11.9 ± 1 | 0.64 ± 0.02 | 19 | — | — | — |
| S177W-N184A | −14.4 ± 0.8 | 0.57 ± 0.02 | 10 | — | — | — |
| S177W-N184M | −14.8 ± 0.9 | 0.57 ± 0.02 | 10 | — | — | — |
| S177W-G180D | −76.8 ± 5 | 0.06 ± 0.01 | 10 | −119.9 ± 5.3 | 0.01 ± 0.002 | 6 |
| S177W-S181D | −9.5 ± 1.2 | 0.69 ± 0.03 | 7 | — | — | — |
| S177W-A185D | −15.6 ± 2.5 | 0.56 ± 0.05 | 5 | — | — | — |
| S177W-V188D | −43.7 ± 1.8 | 0.18 ± 0.01 | 5 | −106.2 ± 6.3 | 0.02 ± 0.007 | 10 |
| S177W-G189D | −19.3 ± 2.3 | 0.5 ± 0.04 | 11 | — | — | — |
The difference in reversal potential (ΔE) that occurred with 90 mM Na+ and 90 mM K+ solutions was measured from the current–voltage relations obtained from recording Xenopus oocytes expressing Kir3.2 channels and corrected for junction potential (4 mV). The relative permeability ratios of Na+ and K+ (PNa/PK) were then deduced by using a form of the Goldman–Hodgkin–Katz voltage equation (see Materials and Methods). For TPNQ-subtracted values, currents were obtained in Na+ before and after addition of 1 μM TPNQ(a mutant blocker), and the difference current was used to determine the reversal potential. n indicates the number of oocytes. Values are mean ± SEM. —, not determined.