Interaction between eukaryotic initiation factors 1A and 5B is required for efficient ribosomal subunit joining

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• Eukaryotic initiation factor 5B (eIF5B) is a GTPase crucial for joining ribosomal subunits during translation initiation.
• GTP hydrolysis by eIF5B releases it from the 80 S initiation complex, allowing translation to proceed.

Purpose of the Study:

• To kinetically analyze GTP hydrolysis by eIF5B within the translation initiation pathway.
• To investigate the role of eukaryotic initiation factor 1A (eIF1A) C terminus in eIF5B activation.

Main Methods:

• Kinetic analysis of GTP hydrolysis by eIF5B.
• Mutagenesis of the eIF1A C-terminal sequence.
• Assays for ribosomal subunit joining.

Main Results:

• eIF5B GTP hydrolysis stimulation depends on early translation initiation steps, including eIF2 GTP hydrolysis.
• The extreme C terminus of eIF1A is essential for full eIF5B GTP hydrolysis activation.
• Disrupting isoleucine residues in the eIF1A C terminus significantly reduces GTP hydrolysis rates and subunit joining.

Conclusions:

• The interaction between the eIF1A C terminus and eIF5B promotes ribosomal subunit joining.
• This interaction may act as a checkpoint for correct 80 S initiation complex formation, ensuring GTP hydrolysis only occurs upon proper assembly.