The ribosome structure controls and directs mRNA entry, translocation and exit dynamics

Area of Science:

• Molecular Biology
• Biophysics
• Structural Biology

Background:

• The ribosome is a complex molecular machine responsible for protein synthesis.
• Ribosomal translocation involves large-scale movements of transfer RNAs (tRNAs) and messenger RNA (mRNA).
• Understanding these dynamics is crucial for comprehending gene expression.

Purpose of the Study:

• To investigate the intrinsic domain motions of the protein-synthesizing ribosome.
• To explore the role of ribosomal proteins and tRNA binding in ribosome dynamics.
• To elucidate the mechanisms of mRNA binding and translocation.

Main Methods:

• Coarse-grained elastic network modeling.
• Normal mode analysis of crystal structures.
• Computational simulation of the 70S ribosomal complex.

Main Results:

• Computed motions confirm known large subunit rotation and small subunit head rotation.
• L1 and L7/L12 stalk flexibility is inherent to ribosomal structure, independent of ribosomal proteins.
• Ribosomal proteins S3, S4, S5, S7, S11, and S18 play roles in mRNA binding, orientation, and fidelity.
• tRNA mobility is influenced by the presence of other tRNAs and specific ribosomal proteins like L1.

Conclusions:

• Ribosome translocation dynamics are primarily governed by its intrinsic shape.
• GTP hydrolysis plays a modulatory role rather than being the sole driver of motion.
• Specific ribosomal proteins are critical for accurate mRNA interaction and translation fidelity.
• The 16S rRNA 3' end acts as a crucial element in mRNA binding during initiation.