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Probing the Molecular Origin of Native-State Flexibility in Repeat Proteins
Sharona S Cohen1, Inbal Riven1, Aitziber L Cortajarena2
1†Chemical Physics Department, Weizmann institute of Science, Rehovot 76100, Israel.
Journal of the American Chemical Society
|July 25, 2015
Summary
Repeat proteins exhibit remarkable elasticity due to their unique structure. This study reveals that hydrophobic inter-repeat contacts, not helix unwinding, drive the spring-like behavior of these proteins.
Area of Science:
- Protein structure and dynamics
- Biophysics
- Molecular biology
Background:
- Repeat proteins possess unique structural properties dominated by short-range interactions.
- This structural characteristic suggests potential elasticity in their native state.
- Understanding the molecular basis of this elasticity is crucial for protein engineering and biomaterials.
Purpose of the Study:
- To investigate the molecular origin of the spring-like behavior in repeat proteins.
- To analyze the structural changes associated with the elasticity of a designed repeat protein (CTPR3).
- To identify the specific interactions responsible for the elastic properties.
Main Methods:
- Single-molecule fluorescence resonance energy transfer (FRET) studies on engineered CTPR3 variants.
- Circular dichroism (CD) spectroscopy.
- Tryptophan fluorescence spectroscopy.
Main Results:
- A continuous expansion of the folded state of CTPR3 was observed at low denaturant concentrations.
- This expansion preceded the transition to the unfolded state, indicating native-state elasticity.
- The expansion was quantitatively explained by a reduction in the protein's spring constant.
- CD and fluorescence spectroscopy confirmed that helix unwinding or intra-repeat interaction unraveling did not occur.
Conclusions:
- Hydrophobic inter-repeat contacts are identified as the primary source of elasticity in repeat proteins.
- The native-state expansion is a key feature of repeat protein elasticity.
- These findings provide insights into the mechanical properties of repeat proteins and their potential applications.
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