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Slow 5F-Trp Dynamics in a Kinetically Trapped Thermodynamically Unstable Protein Probed by Quantitative 19F CEST and
Arathrika Pramanik1, R Aishwarya Bhuvaneshwari1, Ishita Sengupta1
1Department of Chemistry, IIT Bombay Powai, Mumbai 400076, India.
The Journal of Physical Chemistry Letters
|February 13, 2026
Summary
This study reveals that the 19F nucleus in the RfaH protein
Area of Science:
- Biochemistry
- Structural Biology
- Nuclear Magnetic Resonance (NMR) Spectroscopy
Background:
- The C-terminal domain (CTD) of RfaH is a fold-switching protein exhibiting complex dynamics.
- Understanding protein conformational exchange is crucial for deciphering biological function.
Purpose of the Study:
- To investigate the millisecond-second timescale conformational exchange of the RfaH CTD.
- To characterize the dynamics of a kinetically trapped native state using advanced NMR techniques.
Main Methods:
- Quantitative phase-cycled 19F CEST NMR measurements were employed.
- Real-time unfolding, EXSY, and line width analysis were combined for comprehensive data interpretation.
Main Results:
- 19F nucleus exchange was observed between buried and solvent-exposed environments in the native state.
- The osmolyte TMAO and baseline apodization aided in analyzing slow exchange kinetics complicated by protein unfolding.
Conclusions:
- The study successfully distinguished between sparsely populated conformations and globally unfolded species.
- 19F CEST NMR is a powerful tool for probing slow dynamics in complex protein systems.
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