Physics:Proton pump
A proton pump is an integral membrane protein pump that builds up a proton gradient across a biological membrane. Proton pumps catalyzes the following reaction:
- H+[on one side of a biological membrane] + energy ⇌ H+[on the other side of the membrane]
Mechanisms are based on energy-induced conformational changes of the protein structure, or on the Q cycle.
During evolution, proton pumps have arisen independently on multiple occasions. Thus, not only throughout nature, but also within single cells,[clarification needed] different proton pumps that are evolutionarily unrelated can be found. Proton pumps are divided into different major classes of pumps that use different sources of energy, exhibiting different polypeptide compositions and evolutionary origins.
Function
Transport of the positively charged proton is typically electrogenic, i.e.: it generates an electric field across the membrane also called the membrane potential. Proton transport becomes electrogenic if not neutralized electrically by transport of either a corresponding negative charge in the same direction, or a corresponding positive charge in the opposite direction. An example of a proton pump that is not electrogenic, is the proton/potassium pump of the gastric mucosa which catalyzes a balanced exchange of protons and potassium ions.[citation needed]
In cell respiration, the proton pump uses energy to transport protons from the intracellular side to the extracellular side of the plasma membrane.[2] It is an active pump that generates a proton gradient across the membrane. The difference in pH and electric charge (ignoring differences in buffer capacity) creates an electrochemical potential difference that works similar to that of a battery or energy storing unit for the cell.[3] The process could also be seen as analogous to cycling uphill or charging a battery for later use, as it produces potential energy. The proton pump does not create energy, but forms a gradient that stores energy for later use.[4]
Diversity
Electron-transport-driven proton pumps
Electron transport complex I
Electron transport complex III
The cytochrome b6f complex
Electron transport complex IV
ATP-driven proton pumps
Proton pumps driven by adenosine triphosphate (ATP) (also referred to as proton ATPases or H+-ATPases) are proton pumps driven by the hydrolysis of adenosine triphosphate (ATP). Three classes of proton ATPases are found in nature. In a single cell (for example those of fungi and plants), representatives from all three groups of proton ATPases may be present.
P-type proton ATPase
The plasma membrane H+-ATPase is a single subunit P-type ATPase found in the plasma membrane of plants, fungi, protists and many prokaryotes. The plasma membrane H+-ATPase creates the electrochemical gradients in the plasma membrane of plants, fungi, protists, and many prokaryotes. Here, proton gradients are used to drive secondary transport processes. As such, it is essential for the uptake of most metabolites, and also for responses to the environment (e.g., movement of leaves in plants).
V-type proton ATPase
F-type proton ATPase
The F-type proton ATPase is a multi-subunit enzyme of the F-type (also referred to as ATP synthase or FOF1 ATPase). It is found in the mitochondrial inner membrane where it functions as a proton transport-driven ATP synthase.
Pyrophosphate driven proton pumps
Proton pumping pyrophosphatase (also referred to as HH+-PPase or vacuolar-type inorganic pyrophosphatases (V-PPase; V is for vacuolar)) is a proton pump driven by the hydrolysis of inorganic pyrophosphate (PPi). In plants, HH+-PPase is localized to the vacuolar membrane (the tonoplast). This membrane of plants contains two different proton pumps for acidifying the interior of the vacuole, the V-PPase and the V-ATPase.
Light driven proton pumps
Bacteriorhodopsin is a light-driven proton pump used by Archaea, most notably in Haloarchaea. Light is absorbed by a retinal pigment covalently linked to the protein, that results in a conformational change of the molecule that is transmitted to the pump protein associated with proton pumping.[5]
See also
- Active transport
- Chemiosmosis
- Cytochrome
- Protonophore
- Proton-pump inhibitor
- Uncoupler
- 2,4-Dinitrophenol
- V-ATPase
References
- ↑ PDB101: Molecule of the Month: Complex I. doi:10.2210/rcsb_pdb/mom_2011_12. http://pdb101.rcsb.org/motm/144. Retrieved 2025-10-07.
- ↑ Yoshikawa, Shinya; Shimada, Atsuhiro; Shinzawa-Itoh, Kyoko (2015). "Chapter 4, Section 4 Proton Pump Mechanism". in Peter M.H. Kroneck and Martha E. Sosa Torres. Sustaining Life on Planet Earth: Metalloenzymes Mastering Dioxygen and Other Chewy Gases. Metal Ions in Life Sciences. 15. Springer. pp. 108–111. doi:10.1007/978-3-319-12415-5_4. ISBN 978-3-319-12414-8.
- ↑ Campbell, N.A., 2008. Resource Acquisition and Transport in Vascular Plants. 8th ed., Biology. San Francisco: Pearson Benjamin Cummings.
- ↑ Ohnishi, Tomoko (2010). "Piston drives a proton pump". Nature 465 (7297): 428–429. doi:10.1038/465428a. PMID 20505714.
- ↑ Andersson, Magnus; Malmerberg, Erik; Westenhoff, Sebastian; Katona, Gergely; Cammarata, Marco; Wöhri, Annemarie B.; Johansson, Linda C.; Ewald, Friederike et al. (2009-09-09). "Structural Dynamics of Light-Driven Proton Pumps" (in English). Structure 17 (9): 1265–1275. doi:10.1016/j.str.2009.07.007. ISSN 0969-2126. PMID 19748347.
External links
- Proton pump animation
- Proton+Pumps at the US National Library of Medicine Medical Subject Headings (MeSH)
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