Visualizing chaperone-assisted protein folding.

Area of Science:

• Structural Biology
• Biochemistry
• Molecular Dynamics

Background:

• Understanding protein folding mechanisms is crucial for deciphering biological processes.
• Heterogeneous and dynamic protein complexes pose significant structural determination challenges.
• Chaperone-assisted protein folding is vital but poorly understood at a mechanistic level.

Purpose of the Study:

• To develop a novel structural biology approach for visualizing dynamic protein complexes.
• To obtain structural ensembles of chaperone-substrate complexes to understand folding assistance.
• To elucidate the folding landscape of substrate protein immunity protein 7 (Im7) bound to the Spy chaperone.

Main Methods:

• Development of a new X-ray crystallography-based technique: residual electron and anomalous density (READ).
• Application of READ to study the complex of immunity protein 7 (Im7) and Escherichia coli chaperone Spy.
• Visualization of sparsely populated conformations and dynamic folding states of Im7.

Main Results:

• The READ method successfully visualized transient conformations of the Im7-Spy complex.
• A series of snapshots captured the folding progression of Im7 while bound to Spy.
• The study revealed that Spy-bound Im7 explores conformations from unfolded to native-like states.

Conclusions:

• The residual electron and anomalous density (READ) technique provides unprecedented insight into dynamic protein folding.
• Chaperone-assisted folding involves the substrate exploring its conformational landscape while bound.
• This work offers a mechanistic view of how chaperones facilitate protein folding.