TABLE IV.
The RYR2 Inactivation Associated with Various Combinations of Functional States among Its Four Subunits
| Subunit stoichiometry |
i | Opening rate constant, RO |
Closing rate constant, RC |
Probability of stoichiometry PS |
Probability of stoichiometry given closed, PSC |
Probability of stoichiometry given open, PSO |
|---|---|---|---|---|---|---|
| 3I 1O | 1 | φ | θ |  |
 |
 |
| 4I 0O | 2 | φ | λ |  |
 |
 |
| others | 3 | φ | 0 |  |
0 |  |
The kinetic scheme for channel gating is shown in Fig. 10 (scheme 3). States O and I depend on Ca2+ and Mg2+ binding to the I2-site, which is described in Table II B. Three inactivated subunits are needed to permit channel inactivation. Associated with each stoichiometry is the channel opening and closing rate constants, the probability that the channel has that stoichiometry, and the probabilities of the channel open and closed states. Values for the rate constants are given in Table V. The values M and N are normalizing factors:
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