Table 1.
Kinetic parameters of peptide release by methylated and unmethylated release factors on cognate and near-cognate stop codons in the E. coli ribosome in vitro.
| Release Complexes | A site codon | kcat (s-1) | K1/2 (10−6 M) | k cat /K 1/2 | kcat (s−1) | K1/2 (10−6 M) | k cat /K 1/2 |
|---|---|---|---|---|---|---|---|
| RF2m | RF2 | ||||||
| Cognate Complexes | UGA* | 0.083 ± 0.001 | 0.07 ± 0.01 | 1.2 | 0.0091 ± 0.0002 | 0.11 ± 0.01 | 0.08 |
| UAA | 0.108 ± 0.001 | 0.21 ± 0.03 | 0.5 | 0.0052 ± 0.0003 | 0.08 ± 0.03 | 0.07 | |
| Near-cognate complexes | UGG* | 0.0039 ± 0.0006 | 4.10 ± 1.46 | 0.0009 | 0.0010 ± 0.0001 | 4.58 ± 0.76 | 0.0002 |
| RF1 m | RF1 | ||||||
| Cognate complexes | UAG | 1.43 ± 0.03 | 0.07 ± 0.02 | 20 | 0.309 ± 0.008 | 0.08 ± 0.01 | 3.9 |
| UAA | 1.24 ± 0.01 | 0.14 ± 0.01 | 8.8 | 0.289 ± 0.007 | 0.09 ± 0.01 | 3.2 | |
| Near-cognate complexes | UGG | 0.0069 ± 0.0010 | 3.30 ± 0.70 | 0.002 | 0.0027 ± 0.0002 | 3.20 ± 0.40 | 0.0008 |
*Data were taken from the previous study20 for the purpose of comparison. Catalytic rate constants kcat and values of K1/2 were obtained by fitting the observed rates against the corresponding release factor concentrations to the Michaelis–Menten equation. An average of three independent measurements is reported for each reaction and errors are calculated by standard error propagation.