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- The alpha and beta (or A and B) subunits are found in the F1, V1, and A1 complexes of F-, V- and A-ATPases, respectively, as well as flagellar (T3SS) ATPase and the termination factor Rho. The subunits make up a ring that contains the ATP-hydrolyzing (or producing) catalytic core. The F-ATPases (or F1Fo ATPases), V-ATPases (or V1Vo ATPases) and A-ATPases (or A1Ao ATPases) are composed of two linked complexes: the F1, V1 or A1 complex containsthat synthesizes/hydrolyses ATP, and the Fo, Vo or Ao complex that forms the membrane-spanning pore. The F-, V- and A-ATPases all contain rotary motors, one that drives proton translocation across the membrane and one that drives ATP synthesis/hydrolysis. ATPases (or ATP synthases) are membrane-bound enzyme complexes/ion transporters that combine ATP synthesis and/or hydrolysis with the transport of protons across a membrane. ATPases can harness the energy from a proton gradient, using the flux of ions across the membrane via the ATPase proton channel to drive the synthesis of ATP. Some ATPases work in reverse, using the energy from the hydrolysis of ATP to create a proton gradient. There are different types of ATPases, which can differ in function (ATP synthesis and/or hydrolysis), structure (F-, V- and A-ATPases contain rotary motors) and in the type of ions they transport. The types with this domain include:
* F-ATPases (F1Fo ATPases) are found in mitochondria, chloroplasts and bacterial plasma membranes are the prime producers of ATP, using the proton gradient generated by oxidative phosphorylation (mitochondria) or photosynthesis (chloroplasts).
* V-ATPases (V1Vo ATPases) are primarily found in eukaryotic vacuoles, catalysing ATP hydrolysis to transport solutes and lower pH in organelles.
* A-ATPases (A1Ao ATPases) are found in Archaea and function like F-ATPases.
* T3SS / flagellum ATPases, which are homologous to both parts of the A/F/V rotary ATPases: strongly in the "1" part, and weakly in the "O" part.
* Ring-shaped like the Rho factor, where the ring is homologus to the α/β subunits. In F-ATPases, there are three copies each of the alpha and beta subunits that form the catalytic core of the F1 complex, while the remaining F1 subunits (gamma, delta, epsilon) form part of the stalks. There is a substrate-binding site on each of the alpha and beta subunits, those on the beta subunits being catalytic, while those on the alpha subunits are regulatory. The alpha and beta subunits form a cylinder that is attached to the central stalk. The alpha/beta subunits undergo a sequence of conformational changes leading to the formation of ATP from ADP, which are induced by the rotation of the gamma subunit, itself is driven by the movement of protons through the Fo complex C subunit. In V- and A-ATPases, the alpha/A and beta/B subunits of the V1 or A1 complex are homologous to the alpha and beta subunits in the F1 complex of F-ATPases, except that the alpha subunit is catalytic and the beta subunit is regulatory. The alpha/A and beta/B subunits can each be divided into three regions, or domains, centred on the ATP-binding pocket, and based on structure and function. The central domain contains the nucleotide-binding residues that make direct contact with the ADP/ATP molecule. (en)
- As subunidades alfa e beta (ou A e B) são polipeptídeos que juntamente com outras subunidades proteicas constituem a ATP sintase, a enzima que fornece energia para o funcionamento das células. Organizam-se num hexâmero com três subunidades de cada tipo, formando parte dos complexos F1, V1, e A1 dos seguintes tipos de ATPases: , V-ATPases e , respetivamente. Também entram na constituição da e da terminação . As F-ATPases (ou F1FO-ATPases), V-ATPases (ou V1VO-ATPases) e A-ATPases (ou A1AO-ATPases) são compostas por dois complexos ligados: os complexos F1, V1 ou A1 contêm o núcleo catalítico que sintetiza/hidroliza ATP, e os complexos FO, VO ou AO que formam o poro que abrange a membrana. As F-ATPases, V-ATPases e A-ATPases contêm motores rotativos, um que conduz a translocação de protões através da membrana e outro que conduz a síntese/hidrólise de ATP. Nas F-ATPases há três cópias de cada uma das subunidades alfa e beta que formam o centro catalítico do complexo F1, enquanto que as restantes subunidades F1 (gama, delta, épsilon) formam os talos. Tanto as subunidades alfa como as subunidades beta contêm um sítio de ligação do substrato, sendo o da subunidade beta catalítico, enquanto que o das subunidades alfa é regulador. As subunidades alfa e beta formam um cilindro ligado ao eixo central. As subunidades alfa//beta passam por uma sequência de transformações na sua conformação que levam à formação de ATP a partir de ADP, que são induzidas pela rotação da subunidade gama, sendo esta conduzida pelo movimento de protões através da subunidade C do complexo FO. Nas V-ATPases e A-ATPases, as subunidades alfa/A e beta/B dos complexos V1 ou A1 são homólogas das subunidades alfa e beta no complexo F1 das F-ATPases, exceptuando que a subunidade alfa é catalítica e a subunidade beta é reguladora. As subunidades alfa/A e beta/B podem, cada uma, dividirem-se em três regiões, ou domínios, centrados em volta do sítio ativo de ligação do ATP, definidas pela sua estrutura e função. O domínio central contém os resíduos de ligação dos nucleótidos que fazem contato direto com a molécula de ADP/ATP. (pt)
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- The alpha and beta (or A and B) subunits are found in the F1, V1, and A1 complexes of F-, V- and A-ATPases, respectively, as well as flagellar (T3SS) ATPase and the termination factor Rho. The subunits make up a ring that contains the ATP-hydrolyzing (or producing) catalytic core. The F-ATPases (or F1Fo ATPases), V-ATPases (or V1Vo ATPases) and A-ATPases (or A1Ao ATPases) are composed of two linked complexes: the F1, V1 or A1 complex containsthat synthesizes/hydrolyses ATP, and the Fo, Vo or Ao complex that forms the membrane-spanning pore. The F-, V- and A-ATPases all contain rotary motors, one that drives proton translocation across the membrane and one that drives ATP synthesis/hydrolysis. (en)
- As subunidades alfa e beta (ou A e B) são polipeptídeos que juntamente com outras subunidades proteicas constituem a ATP sintase, a enzima que fornece energia para o funcionamento das células. Organizam-se num hexâmero com três subunidades de cada tipo, formando parte dos complexos F1, V1, e A1 dos seguintes tipos de ATPases: , V-ATPases e , respetivamente. Também entram na constituição da e da terminação . (pt)
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