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Quantifying the Initial Unfolding of Bacteriorhodopsin Reveals Retinal Stabilization
Hao Yu1,2, Patrick R Heenan1,3, Devin T Edwards1
1JILA, National Institute of Standards and Technology and University of Colorado, Boulder, CO, 80309, USA.
Angewandte Chemie (International Ed. in English)
|December 18, 2018
Summary
Researchers quantified membrane protein stability using atomic force microscopy. A novel, mechanically stable state in bacteriorhodopsin unfolding was discovered, offering insights into protein energetics.
Area of Science:
- Biophysics
- Structural Biology
- Biochemistry
Background:
- Quantifying forces stabilizing membrane proteins is challenging.
- Initial unfolding events of membrane proteins are poorly understood.
- Understanding these forces is crucial for protein function.
Purpose of the Study:
- To develop a high-precision assay for studying membrane protein unfolding.
- To investigate the initial unfolding dynamics of bacteriorhodopsin.
- To quantify the energetics of membrane proteins under native-like conditions.
Main Methods:
- Developed a high-precision atomic force microscopy (AFM) assay.
- Utilized a cantilever optimized for 2 μs resolution.
- Studied the initial unfolding of bacteriorhodopsin.
Main Results:
- Discovered rapid near-equilibrium folding between the first three unfolding states.
- Identified two transitions corresponding to unfolding of 5 and 3 amino acids.
- Detected a previously unknown, retinal-stabilized, mechanically stable state (150 pN for >1 min).
Conclusions:
- The developed AFM assay allows precise quantification of membrane protein energetics.
- The newly identified state is the most mechanically stable in the bacteriorhodopsin unfolding pathway.
- This work provides a platform for studying native-like membrane protein dynamics.
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