Structural mechanism of mRNA decoding by mammalian GTPase GTPBP1

Area of Science:

• Molecular Biology
• Structural Biology
• Neuroscience

Background:

• GTP-binding protein 1 (GTPBP1) is a translational GTPase related to elongation factor eEF1A.
• GTPBP1 dysfunction is linked to neurodevelopmental errors and human neurodegenerative disorders.
• The precise functions of GTPBP1 in translation and cellular quality control remain largely unknown.

Purpose of the Study:

• To elucidate the structural basis for GTPBP1's function in translation.
• To understand how GTPBP1's unique architecture influences its interaction with the ribosome and tRNA.
• To provide a structural foundation for investigating GTPBP1 mutations in human diseases.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was used to determine the structures of 80S ribosomal complexes.
• Complexes were formed with GTPBP1 bound to aminoacyl-tRNA (aa-tRNA) in the presence of GTP or GDPCP.
• Structural analysis focused on GTPBP1's unique domains and their interactions within the ribosome.

Main Results:

• Cryo-EM structures revealed GTPBP1's unique architecture, including an N-terminal domain and an H-loop.
• These features mediate specific interactions with tRNA and the ribosome, causing slow GTPBP1 dissociation post-GTP hydrolysis.
• This slow dissociation leads to delayed tRNA accommodation, an extended proofreading stage, and enhanced decoding accuracy.

Conclusions:

• GTPBP1's unique structure underlies its slow tRNA delivery and enhanced translational accuracy.
• The findings suggest a role for GTPBP1 in cellular quality control mechanisms.
• Structural insights pave the way for understanding GTPBP1 mutations in neurodegenerative diseases.