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Protein dynamics studied by rotating frame 15N spin relaxation times
T Szyperski1, P Luginbühl, G Otting
1Institut für Molekularbiologie und Biophysik, Eidgenössische Technische Hochschule-Hönggerberg, Zürich, Switzerland.
Journal of Biomolecular NMR
|March 1, 1993
Summary
Investigating protein dynamics in 15N-labeled pancreatic trypsin inhibitor (BPTI) revealed two key conformational changes. These include disulfide bond isomerization and local segmental motions, offering insights into protein flexibility.
Area of Science:
- Biophysics
- Protein Dynamics
- Biochemistry
Background:
- Understanding protein conformational dynamics is crucial for elucidating biological function.
- Bovine pancreatic trypsin inhibitor (BPTI) is a well-characterized model protein for studying molecular interactions and dynamics.
Purpose of the Study:
- To investigate conformational rate processes in aqueous solutions of uniformly 15N-labeled BPTI.
- To characterize the timescales and nature of intramolecular motions within BPTI.
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy was employed.
- Rotating frame relaxation times of backbone 15N spins were measured as a function of spin-lock power.
Main Results:
- Two distinct intramolecular exchange processes were identified.
- A local rate process (correlation time ~1.3 ms) linked to disulfide bond (Cys14-Cys38) isomerization was observed.
- A faster motional mode, potentially local segmental motions (-Cys14-Ala15-Lys16-), was superimposed on the isomerization.
- The overall rotational tumbling correlation time of BPTI was determined to be approximately 2 ns.
Conclusions:
- The study elucidates complex conformational dynamics in BPTI beyond simple rotational tumbling.
- Disulfide bond isomerization and local segmental motions contribute significantly to BPTI's conformational landscape.
- NMR relaxation measurements provide a powerful tool for dissecting multiple dynamic processes in proteins.