|PROSITE documentation PDOC00328|
The sodium pump (Na+,K+ ATPase), located in the plasma membrane of all animal cells , is an heterotrimer of a catalytic subunit (α chain), a glycoprotein subunit of about 34 Kd (β chain) and a small hydrophobic protein of about 6 Kd. The β subunit seems  to regulate, through the assembly of α/β heterodimers, the number of sodium pumps transported to the plasma membrane.
Structurally the β subunit is composed of a charged cytoplasmic domain of about 35 residues, followed by a transmembrane region, and a large extracellular domain that contains three disulfide bonds and glycosylation sites. This structure is schematically represented in the figure below.
+----+ +--+ +-----------+ | | | | | | xxxxxxxxxxxxxxxxxxxxxxxxCxxxxCxCxxCxxxxxxxCxxxxxxxxxxxCxxxx **** **** <-Cyt-><TM><------------Extracellular--------------------->
'C': conserved cysteine involved in a disulfide bond. '*': position of the patterns.
Four isoforms of the β subunit (β-1 to β-4) are currently known.
Gastric (K+, H+) ATPase (proton pump) responsible for acid production in the stomach consist of two subunits ; the β chain is highly similar to the sodium pump β subunits.
We developed two signature patterns for β subunits. The first is located in the cytoplasmic domain, while the second is found in the extracellular domain and contains two of the cysteines involved in disulfide bonds.Last update:
December 2004 / Pattern and text revised.
PROSITE methods (with tools and information) covered by this documentation:
|1||Authors||Horisberger J.D., Lemas V., Kraehenbuhl J.P., Rossier B.C.|
|Title||Structure-function relationship of Na,K-ATPase.|
|Source||Annu. Rev. Physiol. 53:565-584(1991).|
|2||Authors||McDonough A.A., Geering K., Farley R.A.|
|Title||The sodium pump needs its beta subunit.|
|Source||FASEB J. 4:1598-1605(1990).|
|3||Authors||Toh B.-H., Gleeson P.A., Simpson R.J., Moritz R.L., Callaghan J.M., Goldkorn I., Jones C.M., Martinelli T.M., Mu F.-T., Humphris D.C.|
|Title||The 60- to 90-kDa parietal cell autoantigen associated with autoimmune gastritis is a beta subunit of the gastric H+/K(+)-ATPase (proton pump).|
|Source||Proc. Natl. Acad. Sci. U.S.A. 87:6418-6422(1990).|