Structural insights into the translational infidelity mechanism

Area of Science:

• Molecular Biology
• Structural Biology
• Genetics

Background:

• Ribosome-mediated messenger RNA (mRNA) decoding is crucial for protein synthesis but is notably inaccurate.
• Missense errors during translation can lead to non-functional proteins and cellular dysfunction.

Purpose of the Study:

• To elucidate a unified mechanism explaining missense errors during mRNA decoding on the ribosome.
• To investigate the structural basis of tRNA selection and discrimination at the peptidyl-tRNA-binding site.

Main Methods:

• Determination of 11 high-resolution X-ray structures of the 70S ribosome.
• Analysis of ribosome structures in complex with incorrect transfer RNAs (tRNAs) in the decoding center.
• Examination of codon-anticodon duplex geometry and nucleobase interactions.

Main Results:

• Identified specific ribosome structures accommodating mismatched codon-anticodon pairs.
• Observed that G·U mismatches adopt Watson-Crick geometry due to tautomeric shifts or ionization.
• Demonstrated that tRNA binding induces conserved rearrangements in the decoding center, favoring near-Watson-Crick geometries.

Conclusions:

• Missense errors occur when mismatched tRNAs preserve the geometric shape of correct Watson-Crick pairs.
• Geometric selection, driven by tautomerism and ionization, is a dominant mechanism in translational infidelity.
• Understanding this mechanism provides insights into the fidelity of genetic information transfer.