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Quantifying Bacteriorhodopsin Activity as a Function of its Local Environment with a Raman-Based Assay
Ryan E Leighton1, Renee R Frontiera1
1Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States.
The Journal of Physical Chemistry. B
|October 9, 2023
Summary
Researchers developed a new Raman-based assay to study bacteriorhodopsin (bR) proton pump activity within its native membrane. The assay revealed that the cellular environment, specifically extracellular pH, impacts bR function, offering insights into transmembrane protein behavior.
Area of Science:
- Biophysics
- Membrane Protein Function
- Spectroscopy
Background:
- Bacteriorhodopsin (bR) is a light-driven proton pump crucial for halophilic archaea.
- Previous studies on bR photocycle kinetics were limited to purified proteins, excluding native membrane effects.
- Understanding bR function in its native cellular context is essential for elucidating transmembrane protein mechanisms.
Purpose of the Study:
- To develop and validate a novel Raman-based assay for monitoring bacteriorhodopsin activity in situ.
- To investigate the influence of the native membrane environment on the bR photocycle.
- To assess the impact of extracellular pH on bR function within its native membrane.
Main Methods:
- Development of a dual-continuous-wave laser Raman spectroscopy assay.
- Monitoring steady-state depletion of ground-state bR to infer photocycle intermediate populations.
- In vitro and in vivo measurements of bR activity under varying conditions.
Main Results:
- The Raman assay successfully monitored bR activity in vitro and in vivo.
- In vitro results validated the assay's sensitivity to environmental changes.
- In vivo measurements demonstrated decreased bR activity with increasing extracellular pH in the native membrane.
Conclusions:
- The native membrane environment significantly affects bacteriorhodopsin function.
- Extracellular pH is a critical factor influencing bR activity in its natural setting.
- The developed Raman assay provides a powerful tool for future studies on transmembrane protein function in cellular environments.
