Table 2.
Kinetic parameters of EXP-2, voltage-gated K+ channels (Kv), and HERG
| Kv Channels | EXP-2 | HERG | |
|---|---|---|---|
| Activation (msec) | Generally fast | Intermediate | Slow |
| τ at 20 mV | msec range | 54 ± 2 | ~100–300 |
| Inactivation (msec) | Voltage independent, fast and slow | Voltage dependent, ultrafast | Voltage dependent, fast |
| τ at 20 mV | 10s of msec (N type) to sec (C type) | 0.8 ± 0.1, type unknown | ~5–30, C type |
| Deinactivation (msec) | Variable | Fast | Fast |
| τ at −80 mV | ~10–1000 | 5.6 ± 0.7 | ~8 |
| Deactivation (msec) | Fast | Slow | Very slow |
| τ at −80 mV | ~1–10, voltage dependent | 70 ± 3, little voltage-dependent | ~300–1000, Voltage dependent |
| TEA slows inactivation | From inside and outside | From inside | From outside |
| Unit conductance (pS) | Small to intermediate | Large | Small |
| In 100 mM KCl | ~5–25 | 67 ± 2 | 12 |
The data for Kv channels are from Stühmer et al. (1989), Pak et al. (1991a,b), and Grissmer et al. (1994); the data for HERG are from Nakajima et al. (1998), Schönherr et al. (1996), Smith et al. (1996), Spector et al. (1996), Wang et al. (1996 and 1997), and Zou et al. (1997).