Genetically Encoded Pentafluorophenylalanine Enables Quantitative Probing of Local Protein Malleability by 19F NMR

Area of Science:

• Biochemistry
• Structural Biology
• Chemical Biology

Background:

• Aromatic ring flips are fast protein dynamics, difficult to measure quantitatively.
• NMR spectroscopy struggles with the rapid rates of these fluctuations.

Purpose of the Study:

• To develop a method for quantitative measurement of aromatic ring flip kinetics.
• To investigate local structural fluctuations and allosteric effects in proteins.

Main Methods:

• Site-specific genetic incorporation of 2,3,4,5,6-pentafluoro-l-phenylalanine (F5Phe).
• Utilizing 19F NMR spectroscopy to monitor F5Phe ring flips.
• High-resolution X-ray crystallography to confirm structural integrity.
• Pressure-dependent NMR to determine activation volumes.

Main Results:

• F5Phe incorporation slows ring flips by over two orders of magnitude, enabling 19F NMR detection.
• Ring-flip rates vary significantly even within hydrophobic clusters, indicating localized dynamics.
• Small activation volumes suggest spatially confined rearrangements during ring flips.
• Ligand binding and protein interactions modulate ring-flip rates, showing allosteric effects.

Conclusions:

• Fluorinated aromatic amino acids provide a general strategy to engineer protein dynamics.
• Aromatic ring flips are transformed into a broadly applicable probe for local conformational dynamics and allostery.
• This technique offers quantitative insights into protein malleability and allosteric mechanisms.