Related Experiment Videos
Translational accuracy enhanced in vitro by (p)ppGpp
Abstract:
The effect of (p)ppGpp on the accuracy of translation in vitro was studied with a system that has a missense error frequency similar to that of living bacteria. When poly (U) is translated, limitation of the system in Phe increases the Leu missense error frequency. The introduction of (p)ppGpp to the Phe-limited mixtures reduces significantly the missense errors as well as reduces the rate of translation. The introduction of (p)ppGpp to a full system has no effect on the accuracy of translation but does reduce its rate. The effects of (p)ppGpp on rate and accuracy of translation can be simulated in part by other inhibitors of translation such as GDPCP, fusidic acid and tetracycline. Furthermore, the presence of ppGpp or GDPCP in a Phe-limited system leads to an accumulation of Phe-tRNA, while a Phe-limited system that contains only GTP has negligibly small concentrations of Phe-tRNA. We conclude that one way in which (p)ppGpp improves the accuracy of translation is by permitting the system to maintain a favorable Phe-tRNA/Leu-tRNA ratio.
Insights
The stringent response regulator, magic string (p)ppGpp, enhances translation accuracy in bacteria by maintaining optimal aminoacyl-tRNA levels. This molecular mechanism improves protein synthesis fidelity, even under nutrient stress.
Area of Science:
- Molecular Biology
- Bacterial Physiology
- Protein Synthesis
Background:
- Bacterial translation accuracy is crucial for cellular function.
- The stringent response, mediated by magic string (p)ppGpp, is a key bacterial stress response.
- Previous studies suggested a role for (p)ppGpp in regulating translation, but its precise impact on accuracy was unclear.
Purpose of the Study:
- To investigate the effect of magic string (p)ppGpp on in vitro translation accuracy.
- To determine how (p)ppGpp influences missense error frequency and translation rate.
- To elucidate the molecular mechanism by which (p)ppGpp affects translation fidelity.
Main Methods:
- Utilized an in vitro translation system mimicking bacterial missense error rates.
- Manipulated amino acid (phenylalanine) availability and introduced (p)ppGpp.
- Assessed translation accuracy, rate, and aminoacyl-tRNA concentrations.
Main Results:
- Phenylalanine limitation increased leucine missense errors; (p)ppGpp significantly reduced these errors and translation rate.
- (p)ppGpp decreased translation rate in a full system but did not affect accuracy.
- The presence of (p)ppGpp or GDPCP led to increased Phe-tRNA accumulation in Phe-limited systems.
Conclusions:
- Magic string (p)ppGpp enhances translation accuracy by helping maintain a favorable Phe-tRNA/Leu-tRNA ratio.
- This mechanism contributes to improved protein synthesis fidelity under specific cellular conditions.
- The effects of (p)ppGpp on translation can be partially mimicked by other translation inhibitors.