Multivalent Interactions between Chaperone and Ribosome-Nascent Chain Complex Revealed by High-Speed AFM and MD...

Area of Science:

• Molecular Biology
• Biophysics
• Structural Biology

Background:

• Trigger Factor (TF) is a crucial ATP-independent molecular chaperone in bacteria.
• TF assists nascent polypeptide chains emerging from the ribosome during protein synthesis.
• Real-time dynamics of TF during active translation under physiological conditions are not well understood.

Purpose of the Study:

• To visualize the real-time dynamics of TF on *Escherichia coli* ribosomes during active translation.
• To investigate the conformational changes and binding interactions of TF in a near-physiological context.
• To elucidate the role of TF in cotranslational folding.

Main Methods:

• High-speed atomic force microscopy (HS-AFM) for real-time imaging of TF on intact ribosomes.
• All-atom molecular dynamics (MD) simulations to complement experimental observations.
• Visualization of TF interactions with ribosomal proteins uL23 and bL17.

Main Results:

• TF exhibits dynamic transitions between compact and extended conformations.
• TF forms stable and transient contacts with specific ribosomal proteins (uL23 and bL17).
• Multivalent interactions were observed, with TFs engaging distinct sites on the ribosome-nascent chain complex.

Conclusions:

• This study provides unprecedented insights into the real-time dynamics of ribosome-associated chaperones.
• The findings reveal TF's conformational flexibility and multivalent binding capabilities.
• The integrative approach establishes a platform for studying cotranslational folding dynamics.