EF-G catalyzes tRNA translocation by disrupting interactions between decoding center and codon-anticodon duplex

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Ribosome-mediated translation involves elongation factor G (EF-G) catalyzing tRNA-mRNA translocation.
• The precise mechanism by which EF-G initiates translocation remains incompletely understood.

Purpose of the Study:

• To elucidate the role of EF-G in initiating the translocation step of protein synthesis.
• To identify key EF-G domains and interactions critical for breaking the pre-translocation state barrier.

Main Methods:

• Systematic mutagenesis of Escherichia coli EF-G.
• Analysis of inhibitory single-site EF-G mutants.
• Biochemical assays to assess ribosome-tRNA-mRNA complex stability and dynamics.

Main Results:

• Identified pre-translocation (Pre-EF-G) states where tRNAs occupy A/P and P/E sites.
• Discovered that interactions between the decoding center and codon-anticodon duplex form a translocation barrier.
• Demonstrated that conserved loops I and II of EF-G's domain IV disrupt these interactions.

Conclusions:

• EF-G-mediated translocation is initiated by disrupting decoding center-codon-anticodon interactions.
• This disruption by EF-G's domain IV loops triggers subsequent ribosomal rearrangements and tRNA-mRNA movement.
• Provides a mechanistic insight into how EF-G drives the translocation cycle during protein synthesis.