ATPase, V0 complex, subunit d (IPR016727)
Short name: ATPase_V0-cplx_dsu
Overlapping homologous superfamilies
- V-type ATP synthase subunit C-like (IPR036079)
- ATPase, V0 complex, c/d subunit (IPR002843)
- ATPase, V0 complex, subunit d (IPR016727)
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.
V-ATPases (also known as V1V0-ATPase or vacuolar ATPase) (EC:18.104.22.168) are found in the eukaryotic endomembrane system, and in the plasma membrane of prokaryotes and certain specialised eukaryotic cells. V-ATPases hydrolyse ATP to drive a proton pump, and are involved in a variety of vital intra- and inter-cellular processes such as receptor mediated endocytosis, protein trafficking, active transport of metabolites, homeostasis and neurotransmitter release [PMID: 15629643]. V-ATPases are composed of two linked complexes: the V1 complex (subunits A-H) contains the catalytic core that hydrolyses ATP, while the V0 complex (subunits a, c, c', c'', d) forms the membrane-spanning pore. V-ATPases may have an additional role in membrane fusion through binding to t-SNARE proteins [PMID: 15907459].
The V-ATPases (or V1V0-ATPase) and A-ATPases (or A1A0-ATPase) are each composed of two linked complexes: the V1 or A1 complex contains the catalytic core that hydrolyses/synthesizes ATP, and the V0 or A0 complex that forms the membrane-spanning pore. The V- and A-ATPases both contain rotary motors, one that drives proton translocation across the membrane and one that drives ATP synthesis/hydrolysis [PMID: 11309608, PMID: 15629643, PMID: 15168615]. The V- and A-ATPases more closely resemble one another in subunit structure than they do the F-ATPases, although the function of A-ATPases is closer to that of F-ATPases.
This entry represents subunit d from the V0 complex of V-ATPases, which are involved in the translocation of protons across a membrane. There is more than one type of d subunit in V-ATPases, where the D1 subunit is ubiquitous, while the D2 subunit has limited tissue expressivity, possibly to account for differential functions, targeting or regulation of V-ATPase activity [PMID: 15800125].