Ribosome-based protein folding systems are structurally divergent but functionally universal across biological...

Area of Science:

• Molecular Biology
• Cell Biology
• Protein Folding

Background:

• Trigger factor (TF) is a bacterial chaperone that binds nascent polypeptides emerging from ribosomes.
• TF cooperates with the DnaK chaperone system for protein folding in E. coli.
• Eukaryotes, like Saccharomyces cerevisiae, utilize a distinct Hsp70-J complex (Ssb-Ssz-Zuo) for ribosome-associated folding.

Purpose of the Study:

• To investigate the functional similarity between prokaryotic Trigger factor (TF) and eukaryotic Hsp70-J chaperone systems.
• To explore the evolutionary conservation of ribosome-associated protein folding mechanisms.

Main Methods:

• Experimental examination of TF binding to yeast ribosomes.
• Assessing TF's ability to substitute for the functions of the Ssb-Ssz-Zuo complex in yeast.

Main Results:

• Trigger factor (TF) can bind to yeast ribosomes through Rpl25, the counterpart of bacterial ribosomal protein L23.
• TF partially substituted for the functions of the Ssb-Ssz-Zuo complex in yeast, indicating functional conservation.
• Despite structural differences, TF and the yeast Hsp70-based triad perform similar roles in polypeptide folding.

Conclusions:

• Ribosome-associated chaperones exhibit functional conservation across prokaryotes and eukaryotes, despite lacking structural similarity.
• Evolution has utilized divergent molecular components to achieve a common biological design for facilitating protein folding during translation.
• This highlights a fundamental conserved process for efficient gene expression.