TABLE 6.
Tryptophan inhibition of translation beyond the tnaC stop codon in constructs lacking the tnaC-tnaA spacer region
| Strain | Relevant features | Avg β-Gal activity (Miller units) ± SDf
|
+Trp/ −Trpg | |
|---|---|---|---|---|
| −Trp | +Trp | |||
| SVS1144 | tnaC-UGA-tnaA′-′lacZ | 465 ± 42 | 15,728 ± 1,353 | 34 |
| VK100 | tnaC-UGA-′lacZ | 3 | 0.4 | 0.1 |
| VK100/SerUa | VK100 with su UGA (Ser) | 85 ± 6 | 18 ± 2 | 0.2 |
| VK700 | tnaC-UAG-′lacZ | 0.1 | 0.03 | 0.3 |
| VK700/pMY228b | VK700 with su UAG (Trp) | 430 ± 42 | 490 ± 39 | 1 |
| VK700/SerUc | VK700 with su UAG (Ser) | 190 ± 21 | 130 ± 9 | 0.7 |
| VK700/pGFIBId | VK700 with su UAG (His) | 709 ± 63 | 475 ± 48 | 0.6 |
| VK900 | tnaC-UAA-′lacZ | 5 ± 0.5 | 2 ± 0.4 | 0.4 |
| VK900/pSWC115e | VK900 with su UAA (Trp) | 9 ± 1 | 4 ± 0.4 | 0.4 |
a
SerU, Ser-inserting tRNASer UGA suppressor.
b
pMY228, plasmid carrying a Trp-inserting tRNATrp UAG suppressor.
c
SerU, Ser-inserting tRNASer UAG suppressor.
d
pGFIBI, plasmid carrying a His-inserting tRNAHis UAG suppressor.
e
pSWC115, plasmid carrying a Trp-inserting tRNATrp UAA suppressor.
f
Cultures were grown at 37°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.
g
Ratio of activities with and without Trp.