TABLE 1.
Parameters of the fast-gating kinetics of the IP3R
| Gating process | Specific conditions | Parameter symbol | Description | Value |
|---|---|---|---|---|
| Ca2+ binding to its cytosolic activating site Sa | fa unbound to Sfa |  |
Off-rate constant | 65 ± 35 s−1 |
| Ka0 | Dissociation constant | 550 ± 20 nM | ||
| ha0 | Hill coefficient | 1.8 ± 0.1 | ||
| fa bound to Sfa |  |
Off-rate constant | 270 ± 70 s−1 | |
| Ka | Dissociation constant | 12 nM | ||
| ha | Hill coefficient | 2.1 ± 0.1 | ||
| fa binding to Sfa | Ca2+ bound to Sa |  |
On-rate constant to off-rate constant ratio | 3 |
| Ca2+ binding to its cytosolic inhibitory site Si | fi unbound to Sfi |  |
Off-rate constant | 40 ± 15 s−1 |
| Ki0 | Dissociation constant | 45 ± 1 μM | ||
| hi0 | Hill coefficient | 3.2 | ||
| fi bound to Sfi |  |
Off-rate constant | 3 ± 2.5 s−1 | |
| Ki | Dissociation constant | 18 μM | ||
| hi | Hill coefficient | 3.2 | ||
| fi binding to Sfi | Ca2+ bound to Si |  |
On-rate constant | 210 ± 30 s−1 |
 |
Off-rate constant to on-rate constant ratio | 4.5 ± 0.25 |