Proton Release Reactions in the Inward H+ Pump NsXeR.
Luiz Schubert1, Jheng-Liang Chen2, Tobias Fritz3
1Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195Berlin, Germany.
The Journal of Physical Chemistry. B
|September 20, 2023
Summary
Researchers tracked proton movement in xenorhodopsin, an inward proton pump. They found aspartate 220 (D220) is crucial for releasing protons to the cell
Area of Science:
- Membrane biophysics
- Protein structure and function
- Bioenergetics
Background:
- Directional ion transport is vital for cellular functions.
- Bacteriorhodopsin (HsBR) is well-studied for outward proton transport.
- Inward proton pumps like xenorhodopsin (NsXeR) are less understood regarding proton pathways and directionality.
Purpose of the Study:
- To elucidate the protonation pathway and molecular determinants of vectorial proton transport in the light-driven inward proton pump xenorhodopsin (NsXeR).
- To investigate the role of specific residues, particularly D220, in mediating proton release.
Main Methods:
- Combined experimental and theoretical approach.
- Time-resolved infrared spectroscopy to track protonation events.
- Molecular dynamics simulations to model proton pathways.
Main Results:
- Transient deprotonation of D220 was observed concurrently with retinal Schiff base deprotonation.
- A proton release pathway involving a water wire from the retinal Schiff base to D220 was identified.
- D220 acts as a potential gating point for proton release and has allosteric interactions with the retinal Schiff base.
Conclusions:
- D220 plays a key role in mediating proton release to the cytoplasmic side in NsXeR.
- D220 is not the primary proton acceptor of the transiently released proton from the retinal Schiff base.
- Understanding NsXeR's proton pathway provides insights into the mechanism of vectorial proton translocation in inward proton pumps.
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