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Does the ternary complex act as a secondary proton pump and a GTP synthase?
P H Nederkoorn1, H Timmerman, G M Donné-Op den Kelder
1Department of Pharmacochemistry, Faculty of Chemistry, Vrije Universiteit, Amsterdam, The Netherlands.
Trends in Pharmacological Sciences
|May 1, 1995
Summary
G protein-coupled receptors may transport protons, potentially synthesizing GTP from GDP and Pi, similar to ATP synthase. This mechanism could explain physiological effects like signal amplification.
Area of Science:
- Biochemistry
- Cell Biology
- Molecular Pharmacology
Background:
- G protein-coupled receptors (GPCRs) are key cellular signaling molecules.
- Emerging evidence suggests GPCRs may possess proton (H+) transport capabilities.
- The precise mechanisms and physiological relevance of GPCR-mediated proton translocation are under investigation.
Purpose of the Study:
- To review and compare proposed H+ translocation mechanisms in GPCRs.
- To explore the hypothesis that activated GPCRs transport protons from extracellular space to the cytoplasm.
- To discuss the potential role of translocated protons in G protein function and signal amplification.
Main Methods:
- Literature review and synthesis of existing research on GPCRs and proton transport.
- Comparative analysis of proposed H+ translocation pathways.
- Theoretical discussion of G protein-mediated GTP synthesis using translocated protons.
Main Results:
- GPCRs are proposed to function as proton transporters, moving H+ across cell membranes.
- Activated G proteins may utilize these translocated protons to synthesize GTP from GDP and inorganic phosphate (Pi).
- This proton-driven GTP synthesis parallels the function of ATP synthase.
Conclusions:
- GPCRs may play a dual role in signaling and transmembrane proton transport.
- Proton translocation by GPCRs could be a novel mechanism for regulating G protein activity.
- This process may contribute significantly to physiological events, including signal amplification.