| Description | Transmembrane ATPases are membrane-bound enzyme complexes/ion transporters that use ATP hydrolysis to drive the transport of protons across a membrane. Some transmembrane ATPases also work in reverse, harnessing 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.F-ATPases (also known as ATP synthases, F1F0-ATPase, or H(+)-transporting two-sector ATPase) ( ) are composed of two linked complexes: the F1 ATPase complex is the catalytic core and is composed of 5 subunits (alpha, beta, gamma, delta, epsilon), while the F0 ATPase complex is the membrane-embedded proton channel that is composed of at least 3 subunits (A-C), with additional subunits in mitochondria. Both the F1 and F0 complexes are rotary motors that are coupled back-to-back. In the F1 complex, the central gamma subunit forms the rotor inside the cylinder made of the α(3)β(3) subunits, while in the F0 complex, the ring-shaped C subunits forms the rotor. The two rotors rotate in opposite directions, but the F0 rotor is usually stronger, using the force from the proton gradient to push the F1 rotor in reverse in order to drive ATP synthesis [ ]. These ATPases can also work in reverse in bacteria, hydrolysing ATP to create a proton gradient.This entry represents the active site of subunit A (or subunit 6) found in the F0 complex of F-ATPases. This subunit is a key component of the proton channel, and may play a direct role in the translocation of protons across the membrane. Catalysis in the F1 complex depends upon the rotation of the central stalk and F0 c-ring, which in turn is driven by the flux of protons through the membrane via the interface between the F0 c-ring and subunit A. The peripheral stalk links subunit A to the external surface of the F1 domain, and is thought to act as a stator to counter the tendency of subunit A and the F1 α(3)β(3) catalytic portion to rotate with the central rotary element [].Sequence comparison of a subunits from all available sources reveals very few conserved regions. The best conserved region is located in what is predicted to be the fifth transmembrane domain. This region contains three perfectly conserved residues: an arginine, a leucine and an asparagine. Mutagenesis experiments carried out in Escherichia coli [] have shown that the arginine is necessary for proton translocation and that its replacement by another amino acid results in loss of ATPase activity. The signature pattern of this entry contains the arginine residue. | Name | ATP synthase, F0 complex, subunit A, active site |
| Short Name | ATP_synth_F0_asu_AS | Type | Active_site |
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