Proton pump - wikipedia Proton pump This article is about biochemical proton pumps. For generators of proton beams, see synchrotron and cyclotron. A proton pump is an integral membrane protein that builds up a proton gradient across a biological membrane. Proton pumps catalyze the following reaction : H + energy ⇌ H 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, different proton pumps that are evolutionarily unrelated can be found. Proton pumps are divided into different major classes of pumps that utilize different sources of energy, have different polypeptide compositions and evolutionary origins. Contents 1 Function 2 Diversity 3 Electron transport driven proton pumps 3.1 Electron Transport Complex I 3.2 Electron Transport Complex III 3.3 The cytochrome b f complex 3.4 Electron Transport Complex IV 4 ATP driven proton pumps 4.1 P - type proton ATPase 4.2 V - type proton ATPase 4.3 F - type proton ATPase 5 Pyrophosphate driven proton pumps 6 Light driven proton pumps 7 See also 8 References 9 External links Function It should be observed that transport of the positively charged proton typically is electrogenic, i.e. it generates an electrical 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. The combined transmembrane gradient of protons and charges created by proton pumps is called an electrochemical gradient. An electrochemical gradient represents a store of energy ( potential energy ) that can be used to drive a multitude of biological processes such as ATP synthesis, nutrient uptake and action potential formation. In cell respiration, the proton pump uses energy to transport protons from the matrix of the mitochondrion to the inter-membrane space. It is an active pump that generates a proton concentration gradient across the inner mitochondrial membrane because there are more protons outside the matrix than inside. 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. 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. Diversity The energy required for the proton pumping reaction may come from light ( light energy ; bacteriorhodopsins ), electron transfer ( electrical energy ; electron transport complexes I, III and IV ) or energy - rich metabolites ( chemical energy ) such as pyrophosphate ( PPi ; proton - pumping pyrophosphatase ) or adenosine triphosphate ( ATP ; proton ATPases ). Electron transport driven proton pumps Electron transport complex I Main article : NADH dehydrogenase ( ubiquinone ) Complex I ( EC 1.6. 5.3 ) ( also referred to as NADH : ubiquinone oxidoreductase or, especially in the context of the human protein, NADH dehydrogenase ) is a proton pump driven by electron transport. It belongs to the H or Na - translocating NADH Dehydrogenase ( NDH ) Family ( TC # 3. D. 1 ), a member of the Na transporting Mrp superfamily. It catalyzes the transfer of electrons from NADH to coenzyme Q10 ( CoQ10 ) and, in eukaryotes, it is located in the inner mitochondrial membrane. This enzyme helps to establish a transmembrane difference of proton electrochemical potential that the ATP synthase then uses to synthesize ATP. Electron transport complex III Main article : Coenzyme Q -- cytochrome c reductase Complex III ( ( EC 1.10. 2.2 ) ) ( also referred to as cytochrome b 1 or the coenzyme Q : cytochrome c -- oxidoreductase ) is a proton pump driven by electron transport. Complex III is a multisubunit transmembrane protein encoded by both the mitochondrial ( cytochrome b ) and the nuclear genomes ( all other subunits ). Complex III is present in the inner mitochondrial membrane of all aerobic eukaryotes and the inner membranes of most eubacteria. This enzyme helps to establish a transmembrane difference of proton electrochemical potential that the ATP synthase of mitochondria then uses to synthesize ATP. The cytochrome b F complex Main article : Cytochrome b6f complex The cytochrome b f complex ( EC 1.10. 99.1 ) ( also called plastoquinol -- plastocyanin reductase ) is an enzyme related to Complex III but found in the thylakoid membrane in chloroplasts of plants, cyanobacteria, and green algae. This proton pump is driven by electron transport and catalyzes the transfer of electrons from plastoquinol to plastocyanin. The reaction is analogous to the reaction catalyzed by Complex III ( cytochrome bc1 ) of the mitochondrial electron transport chain. This enzyme helps to establish a transmembrane difference of proton electrochemical potential that the ATP synthase of chloroplasts then uses to synthesize ATP. Electron transport complex IV Main article : Cytochrome c oxidase Complex IV ( EC 1.9. 3.1 ) ( also referred to as cytochrome c oxidase ), is a proton pump driven by electron transport. This enzyme is a large transmembrane protein complex found in bacteria and inner mitochondrial membrane of eukaryotes. It receives an electron from each of four cytochrome c molecules, and transfers them to one oxygen molecule, converting molecular oxygen to two molecules of water. In the process, it binds four protons from the inner aqueous phase to make water and in addition translocates four protons across the membrane. This enzyme helps to establish a transmembrane difference of proton electrochemical potential that the ATP synthase of mitochondria then uses to synthesize ATP. ATP driven proton pumps Main article : Proton ATPase Adenosine triphosphate ( ATP ) driven proton pumps ( 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 Main article : Plasma membrane H+ - 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 ). Humans ( and probably other mammals ) have a gastric hydrogen potassium ATPase or H / K ATPase that also belongs to the P - type ATPase family. This enzyme functions as the proton pump of the stomach, primarily responsible for the acidification of the stomach contents ( see gastric acid ). V - type proton ATPase Main article : V - ATPase The V - type proton ATPase is a multisubunit enzyme of the V - type. It is found in various different membranes where it serves to acidify intracellular organelles or the cell exterior. F - type proton ATPase Main article : F - ATPase The F - type proton ATPase is a multisubunit enzyme of the F - type ( also referred to as ATP synthase or F F ATPase ). It is found in the mitochondrial inner membrane where is functions as a proton transport - driven ATP synthase. In mitochondria, reducing equivalents provided by electron transfer or photosynthesis power this translocation of protons. For example, the translocation of protons by cytochrome c oxidase is powered by reducing equivalents provided by reduced cytochrome c. ATP itself powers this transport in the plasma membrane proton ATPase and in the ATPase proton pumps of other cellular membranes. The F F ATP synthase of mitochondria, in contrast, usually conduct protons from high to low concentration across the membrane while drawing energy from this flow to synthesize ATP. Protons translocate across the inner mitochondrial membrane via proton wire. This series of conformational changes, channeled through the a and b subunits of the F particle, drives a series of conformational changes in the stalk connecting the F to the F subunit. This process effectively couples the translocation of protons to the mechanical motion between the Loose, Tight, and Open states of F necessary to phosphorylate ADP. In bacteria and ATP - producing organelles other than mitochondria, reducing equivalents provided by electron transfer or photosynthesis power the translocation of protons. CF ATP ligase of chloroplasts correspond to the human F F ATP synthase in plants. Pyrophosphate driven proton pumps Main article : Proton pumping pyrophosphatase 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 Main article : Bacteriorhodopsin Bacteriorhodopsin is a light - driven proton pump and is used by Archaea, most notably in Halobacteria. Light is absorbed by a retinal pigment covalently linked to the protein, that result in a conformational change of the molecule that is transmitted to the pump protein associated with proton pumping. See also Active transport Chemiosmosis Cytochrome Protonophore Proton - pump inhibitor Uncoupling protein 2, 4 - Dinitrophenol V - ATPase References Jump up ^ 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. Jump up ^ Campbell, N.A., 2008. Resource Acquisition and Transport in Vascular Plants. 8th ed., Biology. San Francisco : Pearson Benjamin Cummings. Jump up ^ Nature, Structural biology : Piston drives a proton pump. by Tomoko Ohnishi, 26 May 2010 External links Proton pump animation Proton Pumps at the US National Library of Medicine Medical Subject Headings ( MeSH ) Membrane transport protein : ion pumps, ATPases / ATP synthase ( TC 3A2 - 3A3 ) F -, V -, and A-type ATPase ( 3. A. 2 ) H ( F - type ) H transporting, mitochondrial : ATP5A1 ATP5B ATP5C1 ATP5C2 ATP5D ATP5E ATP5F1 ATP5G1 ATP5G2 ATP5G3 ATP5H ATP5I ATP5J ATP5J2 ATP5L ATP5L2 ATP5O ATP5S H ( V - type ) H transporting, lysosomal : ATP6AP1 ATP6AP2 ATP6V1A ATP6V1B1 ATP6V1B2 ATP6V1C1 ATP6V1C2 ATP6V1D ATP6V1E1 ATP6V1E2 ATP6V1F ATP6V1G1 ATP6V1G2 ATP6V1G3 ATP6V1H ATP6V0A1 ATP6V0A2 ATP6V0A4 ATP6V0B ATP6V0C ATP6V0D1 ATP6V0D2 ATP6V0E ATP6V0E1 TCIRG1 A-ATPase found in Archea P - type ATPase ( 3. A. 3 ) 3. A. 3.1. 1 : Na / K transporting : ATP1A1 ATP1A2 ATP1A3 ATP1A4 ATP1B1 ATP1B2 ATP1B3 ATP1B4 ATP1G1 3. A. 3.1. 2 : H / K H / K exchanging : ATP4A ATP4B 3. A. 3.1. 4 : H / K transporting, nongastric : ATP12A 3. A. 3.2 : Ca ( SERCA, PMCA, SPCA ) / Ca transporting : ATP2A1 ATP2A2 ATP2A3 ATP2B1 ATP2B2 ATP2B3 ATP2B4 ATP2C1 3. A. 3.5 : Cu transporting : ATP7A ATP7B 3. A. 3.8. 8 : flippase : ATP8A2 Other / ungrouped : Na / K -- H Mg transporting : ATP3 Class I, type 8 : ATP8A1 ATP8B1 ATP8B2 ATP8B3 ATP8B4 Class II, type 9 : ATP9A ATP9B Class V, type 10 : ATP10A ATP10B ATP10D Class VI, type 11 : ATP11A ATP11B ATP11C type 13 : ATP13A1 ATP13A2 ATP13A3 ATP13A4 ATP13A5 see also ATPase disorders Ion pump : proton pumps : Oxidoreduction - driven transporters ( TC 3D ) ETC ETC Complex I ETC Complex III ETC Complex IV Other Cytochrome b6f complex Inorganic pyrophosphatase V - ATPase Retrieved from `` https://en.wikipedia.org/w/index.php?title=Proton_pump&oldid=834143205 '' Categories : Transport proteins Proton Talk Contents About Wikipedia Bosanski Català Čeština Deutsch Español فارسی Français Italiano Nederlands 日本 語 Polski Português Русский Slovenščina 6 more Edit links This page was last edited on 4 April 2018, at 04 : 36. Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. 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Question: what is a proton pump in the human body
Answer: an integral membrane protein that builds up a proton gradient across a biological membrane; an integral membrane protein that builds up a proton gradient across a biological membrane; an integral membrane protein that builds up a proton gradient across a biological membrane