Long-range interdomain communications in eIF5B regulate GTP hydrolysis and translation initiation

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Translation initiation is a key regulatory step in protein synthesis.
• Eukaryotic initiation involves numerous protein factors and GTP-dependent steps.
• The GTPase eIF5B regulates the transition from translation initiation to elongation.

Purpose of the Study:

• To visualize the ribosome-bound conformation of eIF5B.
• To elucidate the mechanism by which eIF5B senses and communicates ribosomal states.
• To identify key residues in eIF5B involved in regulating translation initiation.

Main Methods:

• Electron cryomicroscopy (cryo-EM) to image stalled initiation complexes.
• High-resolution 3D reconstruction of a translation intermediate.
• Site-directed mutagenesis to assess the function of identified residues.

Main Results:

• A high-resolution cryo-EM structure of eIF5B bound to the ribosome was obtained.
• A conserved tyrosine residue (Y837) and its interaction with catalytic histidine (H480) in eIF5B were identified.
• Mutagenesis confirmed the role of these residues in ribosome binding, GTP hydrolysis, and translation initiation.

Conclusions:

• eIF5B utilizes interdomain communication to transmit signals from the P site to the GTPase center.
• The multidomain architecture of translation factors is critical for sensing and communicating ribosomal states.
• This structural and functional insight advances our understanding of eukaryotic translation initiation regulation.