TABLE 2.
Kinetic parameters for RNA stimulated ATPase activity of eIF4A and eIF4F
| kcat | km | |
|---|---|---|
| min−1 | μm | |
| ssRNA stimulated, increasing ATP concentration | ||
| WT eIF4Fa | 1.0 ± 0.7 | 75 ± 50 |
| WT eIF4F | 3.1 ± 1.3 | 160 ± 40 |
| eIF4F ΔRNA1 | 4.5 ± 1.2 | 620 ± 120 |
| eIF4F ΔRNA2 | 5.4 ± 0.5 | 1400 ± 390 |
| eIF4F ΔRNA3 | 4.6 ± 1.1 | 380 ± 45 |
| ssRNA-stimulated, increasing RNA concentration | ||
| WT eIF4Fa | 0.92 ± 0.5 | <0.065 |
| WT eIF4F | 3.1 ± 0.8 | <0.15 |
| eIF4F ΔRNA1 | 4.1 ± 0.5 | <0.15 |
| eIF4F ΔRNA2 | 4.3 ± 0.3 | <0.15 |
| eIF4F ΔRNA3 | 4.5 ± 0.5 | <0.15 |
| dsRNA-stimulated, increasing ATP concentration | ||
| eIF4A | 0.2 ± 0.05 | 225 ± 50 |
| WT eIF4F | NDb | ND |
| eIF4F ΔRNA1 | 5.9 ± 2.0c | 3270 ± 680c |
| eIF4F ΔRNA2 | 3.2 ± 0.4c | 2100 ± 150c |
| eIF4F ΔRNA3 | 4.4 ± 1.1c | 4100 ± 900c |
a Measured with capped RNA.
b ND means not determined because of low signal to noise with the slow rates observed.
c Values were projected from fits; all errors shown are mean deviations; n ≥ 2.