InterPro domain: IPR038495

This entry represents a domain found in subunit E from V-ATPases and A-ATPase/synthases. Subunit E appears to form a tight interaction with subunit G, which together may act as stators to prevent certain subunits from rotating with the central rotary element, much in the same way as the F0 complex subunit B does in F-ATPases [ 1 ]. In addition to its key role in stator structure, subunit E appears to have a role in mediating interactions with putative regulatory subunits [ 2 ].

Subunit E is a long, two domain protein with a C-terminal globular domain [ 3 , 4 ]. It contains hendecad repeats (11/3) along the entirety of its N-terminal helix. The hendecad pattern is of the form a-b-c-d-e-f-g-h-i-j-k, with hydrophobic residues at positions a,d,e,h resulting in a right handed coiling of the helices [ 5 ]. The C-terminal half of subunit E forms the majority of the head group and consists of a globular domain, which contains a four-stranded b-sheet and two a-helices followed by a C-terminal a-helical tail [ 6 ].

Proton-translocating ATPases (H+-ATPases) are rotary enzymes that couple proton (or Na+) translocation across membranes with ATP synthesis or hydrolysis. There are three types of these protein complexes: F-, V- and A-type ATPases. F-type ATPases, better known as F1F0 ATP synthases, use energy from proton translocation across an electrochemical gradient to synthesize ATP. In contrast, vacuolar or V-type ATPases work in reverse by actively pumping protons through membranes using energy derived from ATP hydrolysis. Although eukaryotes contain both F- and V-ATPases, each highly specialized in its physiological function, archaea and eubacteria typically contain only one complex. Most eubacteria contain F-type ATPases, but some eubacteria and all known archaea contain complexes that are evolutionary closer to V-ATPases and are referred to as A-ATPases/synthases [ 6 ].

1. Building the stator of the yeast vacuolar-ATPase: specific interaction between subunits E and G. J. Biol. Chem. 279, 40670-6
2. Defined sites of interaction between subunits E (Vma4p), C (Vma5p), and G (Vma10p) within the stator structure of the vacuolar H+-ATPase. Biochemistry 44, 3933-41
3. Crystal and solution structure of the C-terminal part of the Methanocaldococcus jannaschii A1AO ATP synthase subunit E revealed by X-ray diffraction and small-angle X-ray scattering. J. Bioenerg. Biomembr. 42, 311-20
4. The structure of the peripheral stalk of Thermus thermophilus H+-ATPase/synthase. Nat. Struct. Mol. Biol.
5. Crystal Structure of the Yeast Vacuolar ATPase Heterotrimeric EGC(head) Peripheral Stalk Complex. Structure 17, 373-8