Table 1.
Kinetics of the activation of WT-RMPK and K114Q mutant by monovalent cations at saturating concentrations of PEP3−, Mg-ADP complex, and Mg2+free.The data from Figure 3A were fitted to the Michaelis–Menten equation (v = Vmax S/Km + S) and to the Hill equation (v = Vmax Sn/K0.5n+ Sn) (Origin version 7.0). The mean and standard deviation from three experiments are shown. kcat/aK values are expressed in log form.
| M+.Ionic radius (pm) | WT-RMPK | K114Q | ||||||
|---|---|---|---|---|---|---|---|---|
| kcat (s−1) | K (mM) | n | log E (s−1 M−1) | kcat (s−1) | K (mM) | n | log E (s−1 M−1) | |
| Li+69 | 16 ± 3 | 53 ± 25 | ___ | 0.47 | N.D. | N.D. | N.D. | N.D. |
| Na+102 | 138 ± 8 | 48 ± 4 | 1.7 ± 0.1 | 3.46 | N.D. | N.D. | N.D. | N.D. |
| K+138 | 857 ± 16 | 5.8 ± 0.2 | 1.5 ± 0.1 | 5.17 | 970 ± 24 | 11 ± 0.6 | 1.4 ± 0.1 | 4.95 |
| NH4+147 | 596 ± 24 | 2.5 ± 0.2 | 1.8 ± 0.2 | 5.38 | 742 ± 25 | 3.5 ± 0.2 | 1.6 ± 0.1 | 5.33 |
| Rb+148 | 462 ± 20 | 5.4 ± 0.4 | 1.4 ± 0.2 | 4.93 | 691 ± 24 | 7.0 ± 0.5 | 1.5 ± 0.1 | 4.99 |
| Cs+170 | 198 ± 12 | 20 ± 3 | 1.5 ± 0.1 | 3.99 | 223 ± 13 | 15 ± 1.8 | 1.4 ± 0.2 | 4.17 |
aK represents the K0.5 and Km for the data fitted to the Hill and Michaelis–Menten equations, respectively.