ATPase, A1 complex, epsilon subunit, archaeal (IPR012508)
Short name: ATPase_A1-cplx_e-su
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.
There are several different types of transmembrane ATPases, which can differ in function (ATP hydrolysis and/or synthesis), structure (e.g., F-, V- and A-ATPases, which contain rotary motors) and in the type of ions they transport [PMID: 15473999, PMID: 15078220]. The different types include:
- F-ATPases (ATP synthases, F1F0-ATPases), which are found in mitochondria, chloroplasts and bacterial plasma membranes where they are the prime producers of ATP, using the proton gradient generated by oxidative phosphorylation (mitochondria) or photosynthesis (chloroplasts).
- V-ATPases (V1V0-ATPases), which are primarily found in eukaryotes and they function as proton pumps that acidify intracellular compartments and, in some cases, transport protons across the plasma membrane [PMID: 20450191]. They are also found in bacteria [PMID: 9741106].
- A-ATPases (A1A0-ATPases), which are found in Archaea and function like F-ATPases, though with respect to their structure and some inhibitor responses, A-ATPases are more closely related to the V-ATPases [PMID: 18937357, PMID: 1385979].
- P-ATPases (E1E2-ATPases), which are found in bacteria and in eukaryotic plasma membranes and organelles, and function to transport a variety of different ions across membranes.
- E-ATPases, which are cell-surface enzymes that hydrolyse a range of NTPs, including extracellular ATP.
A-ATPases (or A1A0-ATPase) (EC:184.108.40.206) are found exclusively in Archaea and display a close resemblance in structure and subunit composition with V-ATPases, although their function in both ATP synthesis and ATP hydrolysis is closer to that of F-ATPases [PMID: 10340845]. A-ATPases are composed of two linked complexes: the A1 complex consisting of seven subunits contains the catalytic core that synthesizes/hydrolyses ATP, while the A0 complex consisting of at least two subunits forms the membrane-spanning pore [PMID: 8702544]. The rotary motor in A-ATPases is composed of only two subunits, the stator subunit I and the rotor subunit C [PMID: 15168615]. A-ATPases may have arisen as an adaptation to the different cellular needs and the more extreme environmental conditions faced by Archaeal species.
The epsilon subunit is the smallest (7 kDa) of those found in the A1 complex. Unlike the A, B and C subunits, the epsilon subunit does not have a homologous counterpart in F- or V-ATPases [PMID: 2147683].