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Updated: Jun 14, 2025
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Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
Published on: June 27, 2014
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Driving forces of proton-pumping rhodopsins
Akari Okuyama1, Shoko Hososhima2, Hideki Kandori2
1Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Nagoya, Aichi, Japan.
Biophysical Journal
|September 7, 2024
Summary
Proton-pumping rhodopsins, essential for creating cellular energy gradients, show diverse transport capabilities. Their driving forces vary significantly, influenced by environmental factors and evolutionary adaptations.
Area of Science:
- Biochemistry
- Biophysics
- Microbiology
Background:
- Proton-pumping rhodopsins are microbial light-driven proton transporters.
- They are classified as outward- or inward-directed proton pumps.
- Both pump types actively generate a proton (H+) gradient across membranes.
Purpose of the Study:
- To investigate the driving force of proton-pumping rhodopsins.
- To assess the impact of membrane potential (ΔΨ) and pH gradient (ΔpH) on their function.
- To characterize H+ transport properties of diverse rhodopsins.
Main Methods:
- Systematic characterization of nine proton-pumping rhodopsins (six outward, three inward).
- Expression of rhodopsins in mammalian cells.
- Patch-clamp measurements to determine current-voltage (I-V) relations and estimate driving force.
Main Results:
- A wide range of driving forces (83–399 mV) was observed among the tested rhodopsins.
- A strong correlation was found between pump driving force and current decay rate.
- pH dependency was generally lower than predicted by the Nernst potential for most rhodopsins.
Conclusions:
- Proton-pumping rhodopsins exhibit significant variations in driving force, kinetics, and pH sensitivity.
- These diverse properties likely reflect evolutionary adaptations to different environmental conditions.
- Understanding these variations is crucial for harnessing rhodopsins in biotechnological applications.
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