Hydration dependence of active core fluctuations in bacteriorhodopsin
Kathleen Wood1, Ursula Lehnert, Brigitte Kessler
1Institut Laue-Langevin, BP 156, F-38042 Grenoble cedex 9, France.
Biophysical Journal
|March 15, 2008
Summary
Investigating bacteriorhodopsin (BR) dynamics using neutron scattering reveals that larger amplitude motions are crucial for function. Lowering hydration inhibits these motions, slowing proton pumping activity.
Area of Science:
- Biophysics
- Structural Biology
- Membrane Proteins
Background:
- Bacteriorhodopsin (BR) is a key light-driven proton pump in purple membranes.
- Understanding the dynamics of BR is essential for elucidating its proton pumping mechanism.
Purpose of the Study:
- To investigate the thermal dynamics of isotope-labeled amino acids and retinal in bacteriorhodopsin.
- To characterize the dynamical response of BR to hydration levels.
Main Methods:
- Neutron scattering with hydrogen-deuterium labeling on two spectrometers.
- Analysis of isotope-labeled amino acids, retinal, and the purple membrane.
Main Results:
- Two populations of motion were identified in BR.
- Larger amplitude dynamics of labeled components were more resilient than the membrane.
- BR's labeled components are not shielded from hydration effects.
Conclusions:
- High-amplitude motions in BR are functionally important.
- Inhibiting these motions by reducing hydration slows the photocycle and proton pumping.
- Hydration plays a critical role in regulating BR's activity.
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