PROSITE documentation PDOC00328Sodium and potassium ATPases beta subunits signatures
The sodium pump (Na+,K+ ATPase), located in the plasma membrane of all animal cells [1], 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 [2] 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 [3]; 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.
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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). | |
PubMed ID | 1645948 | |
DOI | 10.1146/annurev.ph.53.030191.003025 |
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). | |
PubMed ID | 2156741 |
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). | |
PubMed ID | 1974721 |
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