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Updated: Mar 8, 2026

High-Resolution Neutron Spectroscopy to Study Picosecond-Nanosecond Dynamics of Proteins and Hydration Water
Published on: April 28, 2022
Time-resolved neutron scattering provides new insight into protein substrate processing by a AAA+ unfoldase
Ziad Ibrahim1,2,3,4, Anne Martel4, Martine Moulin4
1Université Grenoble Alpes, Institut de Biologie Structurale, 38044 Grenoble, France.
This study introduces a novel method to track protein unfolding and complex structural changes during biochemical reactions in real-time. The technique revealed how AAA+ ATPases mechanically unfold substrates via a reversible power stroke mechanism.
Area of Science:
- Biochemistry
- Structural Biology
- Biophysics
Background:
- Studying dynamic structural changes in macromolecular complexes during reactions is challenging.
- Existing methods often lack the time resolution to capture rapid molecular events.
Purpose of the Study:
- To develop and demonstrate a novel time-resolved approach for analyzing structural dynamics of protein complexes and substrates during biochemical reactions.
- To elucidate the mechanism of substrate unfolding by archaeal AAA+ PAN unfoldase.
Main Methods:
- Combined small-angle neutron scattering, deuterium labeling, contrast variation, temperature activation, and fluorescence spectroscopy.
- Applied the method to study the mechanical unfolding of green fluorescent protein by PAN unfoldase on a sub-minute timescale.
Main Results:
- Monitored the real-time mechanical unfolding of a green fluorescent protein substrate.
- Observed energy-dependent conformational changes (contraction and expansion) in the PAN complex during substrate unfolding.
- Characterized the reaction kinetics on the sub-minute timescale.
Conclusions:
- The results support a reversible power stroke mechanism for substrate unfolding by AAA+ ATPases.
- The developed time-resolved approach is broadly applicable to studying protein remodeling complexes and their substrates.
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