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Release factor-dependent false stops are infrequent in Escherichia coli
F Jørgensen1, F M Adamski, W P Tate
1Department of Molecular Biology University of Uppsala, Sweden.
Journal of Molecular Biology
|March 5, 1993
Summary
Researchers quantified "false stop" events, where sense codons are mistranslated as stop codons. Elevated release factor 1 (RF1) significantly reduced translational processivity, suggesting low false stop frequencies in cells.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Translation fidelity is crucial for cellular function.
- Mistranslation of sense codons as stop codons, termed "false stops," can disrupt protein synthesis.
- Release factors (RFs) mediate termination of translation.
Purpose of the Study:
- To estimate the frequency of release factor-dependent "false stop" events.
- To investigate the role of RF1 and RF2 in translational errors.
Main Methods:
- Utilized a plasmid expression system to overproduce RF1 and RF2.
- Employed a lacZ processivity assay to measure translational fidelity.
- Correlated release factor concentrations with loss of translational processivity.
Main Results:
- A 30- to 40-fold increase in RF1 concentration reduced lacZ processivity from 0.6 to 0.3.
- Extrapolation suggested a false stop frequency of approximately 10^-5 per codon under normal RF1 levels.
- A threefold increase in RF2 concentration had no significant effect on lacZ processivity.
Conclusions:
- False stop events mediated by RF1 are infrequent compared to other translation errors.
- RF1 appears to play a more significant role in translational fidelity than RF2.
- These findings contribute to understanding the accuracy of the cellular translation machinery.