Specific interaction between EF-G and RRF and its implication for GTP-dependent ribosome splitting into subunits

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Bacterial protein synthesis termination involves ribosome recycling.
• Ribosome recycling factor (RRF) and elongation factor G (EF-G) mediate subunit dissociation.
• Previous models proposed EF-G-induced RRF rotation destabilizes intersubunit bridges.

Purpose of the Study:

• To elucidate the structural mechanism of ribosome subunit splitting by EF-G and RRF.
• To visualize the EF-G-RRF complex on the 50S ribosomal subunit.
• To understand the role of GTP hydrolysis in ribosome recycling.

Main Methods:

• Cryo-electron microscopy (cryo-EM) at 9 Å resolution.
• Generation of a quasi-atomic model of the 50S x EF-G x GTP analogue x RRF complex.
• Comparative analysis of EF-G structures in different states.

Main Results:

• A detailed cryo-EM map and model of the 50S x EF-G x GTP analogue x RRF complex were obtained.
• The interaction between EF-G and RRF on the 50S subunit was visualized.
• A conformational change in EF-G's Switch I region was observed, linking GTP hydrolysis to RRF domain rotation.

Conclusions:

• EF-G binding and GTP hydrolysis induce RRF head domain rotation via signal transduction.
• This rotation destabilizes intersubunit bridges, leading to ribosome subunit separation.
• The findings validate structural models and known mutations in EF-G and RRF.