A flexible loop in yeast ribosomal protein L11 coordinates P-site tRNA binding

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Ribosomal protein L11 (and homologs like L5) possesses a conserved internal loop.
• This loop, termed the L11 P-site loop, interacts with the peptidyl-transfer RNA (tRNA) T-loop.

Purpose of the Study:

• To investigate the function and structural dynamics of the L11 P-site loop.
• To understand how the P-site loop's interaction with tRNA influences ribosomal function.

Main Methods:

• High-resolution structural analysis of yeast ribosomes.
• Chemical protection assays to study loop flexibility.
• Site-directed mutagenesis to create P-site loop variants.

Main Results:

• The P-site loop is flexible, extending into the P-site when unoccupied and retracting when occupied by tRNA.
• Mutants altering P-site loop conformation showed altered peptidyl-tRNA and aminoacyl-tRNA binding affinities.
• Functional consequences included changes in translational fidelity, drug sensitivity, and cell growth.

Conclusions:

• The L11 P-site loop acts as a dynamic sensor of P-site occupancy.
• This monitoring mechanism is crucial for optimizing ribosome function, including translation accuracy and cellular fitness.