Conserved conformational selection mechanism of Hsp70 chaperone-substrate interactions

Area of Science:

• Biochemistry and Molecular Biology
• Structural Biology
• Cellular Biology

Background:

• Molecular recognition is fundamental to biological processes, often involving ligand binding to specific conformations.
• Two models describe ligand-target interactions: conformational selection (CS) and induced fit (IF).
• Heat shock protein 70 (Hsp70) chaperones maintain cellular proteome integrity via ATP-dependent client protein interactions.

Purpose of the Study:

• To directly quantify the contributions of conformational selection (CS) and induced fit (IF) pathways in Hsp70 chaperone-client interactions.
• To investigate the conserved mechanisms of client recognition by Hsp70 chaperones across species.

Main Methods:

• Utilized solution Nuclear Magnetic Resonance (NMR) spectroscopy.
• Employed methyl TROSY (transverse relaxation-optimized spectroscopy) effect for enhanced spectral resolution.
• Applied selective isotope-labeling methodologies for precise structural and dynamic analysis.

Main Results:

• Demonstrated that both bacterial and human Hsp70 chaperones preferentially bind to the unfolded state of client proteins.
• Provided direct quantitative evidence for the flux along CS and IF pathways during Hsp70 binding.
• The findings indicate that Hsp70 selects clients from a pre-existing ensemble of interconverting conformations.

Conclusions:

• Hsp70 chaperones utilize a conserved conformational selection mechanism for client recognition.
• The study highlights the critical role of molecular dynamics in the Hsp70-mediated recognition process.
• This conserved recognition mode is essential for maintaining cellular proteome homeostasis.