InterPro domain: IPR035921

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 [ 1 , 2 ]. 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 [ 3 ]. They are also found in bacteria [ 4 ].
• 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 [ 5 , 6 ].
• 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.

The F-ATPases (or F1F0-ATPases) and V-ATPases (or V1V0-ATPases) are each composed of two linked complexes: the F1 or V1 complex contains the catalytic core that synthesizes/hydrolyses ATP, and the F0 or V0 complex that forms the membrane-spanning pore. The F- and V-ATPases all contain rotary motors, one that drives proton translocation across the membrane and one that drives ATP synthesis/hydrolysis [ 7 , 8 ].

In V-ATPases, there are three proteolipid subunits (c, c' and c'') that form part of the proton-conducting pore, each containing a buried glutamic acid residue that is essential for proton transport, and together they form a hexameric ring spanning the membrane [ 9 , 10 ].

Structurally, the c subunits consist of a two antiparallel transmembrane helices. Both helices of one c subunit are connected by a loop on the cytoplasmic side [ 11 ].

This entry represents the V-ATPase proteolipid subunit C like domain found in the V-ATPase proteolipid subunit C and the F-ATP synthase subunit C.

1. The evolution of A-, F-, and V-type ATP synthases and ATPases: reversals in function and changes in the H+/ATP coupling ratio. FEBS Lett. 576, 1-4
2. Mechanisms of ATPases--a multi-disciplinary approach. Curr. Protein Pept. Sci. 5, 89-105
3. Regulation and isoform function of the V-ATPases. Biochemistry 49, 4715-23
4. F-and V-ATPases in the genus Thermus and related species. Syst. Appl. Microbiol. 21, 12-22
5. New insights into structure-function relationships between archeal ATP synthase (A1A0) and vacuolar type ATPase (V1V0). Bioessays 30, 1096-109
6. F-type or V-type? The chimeric nature of the archaebacterial ATP synthase. Biochim. Biophys. Acta 1101, 232-5
7. Resolution of distinct rotational substeps by submillisecond kinetic analysis of F1-ATPase. Nature 410, 898-904
8. A structural model of the vacuolar ATPase from transmission electron microscopy. Micron 36, 109-26
9. Cysteine-mediated cross-linking indicates that subunit C of the V-ATPase is in close proximity to subunits E and G of the V1 domain and subunit a of the V0 domain. J. Biol. Chem. 280, 27896-903
10. Structure and function of the vacuolar H+-ATPase: moving from low-resolution models to high-resolution structures. J. Bioenerg. Biomembr. 35, 337-45
11. High-resolution structure of the rotor ring of a proton-dependent ATP synthase. Nat. Struct. Mol. Biol. 16, 1068-73