Two proofreading steps amplify the accuracy of genetic code translation.

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• Ribosome-mediated selection of aminoacyl-tRNAs (aa-tRNAs) is crucial for accurate protein synthesis.
• Elongation factor Tu (EF-Tu) plays a key role in delivering aa-tRNAs to the ribosome.
• A proofreading mechanism ensures the fidelity of aa-tRNA selection.

Purpose of the Study:

• To investigate the stepwise mechanism of aa-tRNA proofreading by the ribosome.
• To elucidate the role of EF-Tu affinity in the accuracy of aa-tRNA selection.
• To identify the molecular basis of proofreading in bacterial translation.

Main Methods:

• Utilized tRNA mutants with varying affinities for EF-Tu.
• Analyzed aa-tRNA selection and proofreading in a reconstituted in vitro system.
• Investigated the dependence of proofreading steps on EF-Tu and GTP hydrolysis.

Main Results:

• Demonstrated that aa-tRNA proofreading occurs in two distinct, consecutive steps.
• Showed that the initial selection step's accuracy correlates linearly with aa-tRNA affinity for EF-Tu·GDP.
• Identified a second, EF-Tu-independent proofreading step after EF-Tu·GDP dissociation.

Conclusions:

• Bacterial aa-tRNA proofreading is a multi-step process involving EF-Tu-dependent and independent stages.
• EF-Tu affinity is critical for the accuracy of the initial aa-tRNA selection.
• The findings reveal the molecular basis of translational fidelity and the importance of multistep selection in biological information processing.