TABLE 1.
Kinetic parameters of aminoacylation with unmodified transcripts of tRNACys
| tRNA | CysRS | Km (μM) | kcat (sec−1) | kcat/Km (M−1 sec−1) | Fold |
|---|---|---|---|---|---|
| The steady-state parameters Km and kcat were determined with catalytic enzyme concentrations that were at least 20-fold below the lowest concentrations of a given tRNA substrate. This amounted to 0.5–1.0 nM E. coli (Ec) or human (Hs) CysRS with 0.2–6 μM tRNA and 3–7 nM Halobacterium sp. NRC-1 CysRS with 0.5–8 μM wild-type tRNA and 5–100 μM mutant tRNAs. The parameters for E. coli CysRS (Christian et al. 2000) and human CysRS (Davidson et al. 2001) were published previously. | |||||
| Ec tRNACys | E. coli | 1.16 ± 0.01 | 2.46 ± 0.06 | 2.12 × 106 | 8.0 |
| Hs tRNACys | Human | 1.4 ± 0.1 | 1.5 ± 0.1 | 1.01 × 106 | 3.8 |
| Hsp tRNACys, wt | Hsp | 1.39 ± 0.20 | 0.36 ± 0.13 | 2.65 × 105 | 1.0 |
| Hsp, U73G | Hsp | — | — | 4.3 | 1.7 × 10−5 |
| Hsp, CUG anticodon | Hsp | 53.1 ± 15.6 | (1.7 ± 0.4) × 10−3 | 35.9 | 1.4 × 10−4 |
| Hsp, A12G | Hsp | 27.2 ± 0.85 | (9.0 ± 0.9) × 10−3 | 3.33 × 102 | 1.3 × 10−3 |
| Hsp, C23U | Hsp | 9.92 ± 1.05 | (7.8 ± 0.2) × 10−2 | 7.96 × 103 | 3.0 × 10−2 |
