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A multifrequency electron spin resonance study of T4 lysozyme dynamics
J P Barnes1, Z Liang, H S Mchaourab
1Baker Laboratory of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301, USA.
Biophysical Journal
|June 4, 1999
Summary
Electron spin resonance (ESR) spectroscopy reveals distinct motion modes in T4 lysozyme. These findings offer insights into enzyme dynamics and local structural ordering using advanced ESR techniques.
Area of Science:
- Biophysics
- Enzymology
- Spectroscopy
Background:
- T4 lysozyme is a well-studied enzyme.
- Understanding enzyme dynamics is crucial for function.
- Nitroxide spin probes are effective for studying biomolecular motion.
Purpose of the Study:
- To investigate the dynamics and local structural ordering of T4 lysozyme.
- To analyze the motion of nitroxide-labeled enzyme derivatives.
- To explore temperature-dependent changes in enzyme structure and dynamics.
Main Methods:
- Electron spin resonance (ESR) spectroscopy at 250 GHz and 9 GHz.
- Utilizing nitroxide-labeled T4 lysozyme derivatives at sites 44 and 69.
- Applying the microscopic ordering with macroscopic disordering (MOMD) and slowly relaxing local structure (SRLS) models.
Main Results:
- 250-GHz ESR spectra fit well with the MOMD model, accounting for tether influence.
- 9-GHz ESR spectra require the SRLS model, incorporating overall rotational diffusion.
- Simultaneous fitting of both 250-GHz and 9-GHz spectra was achieved.
- Two distinct motional/ordering modes of the probe were identified for both lysozyme derivatives.
- The probe exhibits faster diffusion around an axis perpendicular to its tether.
Conclusions:
- The tether connecting the spin probe to T4 lysozyme exists in at least two distinct conformations.
- Enzyme dynamics can be effectively characterized by combining high and low frequency ESR data.
- Local fluctuations of the peptide backbone likely contribute to the observed probe diffusion.