TABLE 5.
Introducing the UGA stop codon in the −1 or +1 reading frame immediately following tnaC-UAG does not appreciably alter the response to prfA1
| Strain | Relevant featuresa | Avg β-Gal activity (Miller units) ± SDb
|
+Trp/ −Trpc | |
|---|---|---|---|---|
| −Trp | +Trp | |||
| VK800 | tnaC-UAG-tnaA′-′lacZ | 52 ± 4 | 1,218 ± 164 | 23 |
| VK801 | VK800 prfA1 | 953 ± 83 | 3,090 ± 434 | 3.2 |
| VK1100 | tnaC-UAG UUUGCC to tnaC-UAG UUUGAC | 182 ± 15 | 1,270 ± 101 | 7 |
| VK1101 | VK1100 prfA1 | 953 ± 118 | 2,074 ± 300 | 2.2 |
| VK1200 | tnaC-UAG UUUGCC to tnaC-UAG UUGACC | 27 ± 5 | 857 ± 94 | 32 |
| VK1201 | VK1200 prfA1 | 261 ± 18 | 841 ± 81 | 3.2 |
a
Underlined changes introduce stop codons in the −1 or +1 reading frame following tnaC-UAG. The out-of-frame UGA stop codon is in boldface type.
b
Cultures were grown at 30°C in minimal medium (49) plus 0.2% glycerol and 0.05% acid-hydrolyzed casein, with (+Trp) or without (−Trp) 100 μg of l-Trp per ml. For β-Gal assay conditions, see Materials and Methods. Values are for at least five cultures of each type.
c
Ratio of activities with and without Trp.