{PDOC00328}
{PS00390; ATPASE_NA_K_BETA_1}
{PS00391; ATPASE_NA_K_BETA_2}
{BEGIN}
*********************************************************
* Sodium 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  (alpha  chain), a
glycoprotein subunit  of  about  34  Kd  (beta  chain) and a small hydrophobic
protein of  about  6 Kd.   The beta subunit seems [2] to regulate, through the
assembly  of alpha/beta   heterodimers, the number of sodium pumps transported
to the plasma membrane.

Structurally the beta 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 beta subunit (beta-1 to beta-4) are currently known.

Gastric (K+,  H+)  ATPase (proton pump) responsible for acid production in the
stomach consist  of  two subunits [3]; the beta chain is highly similar to the
sodium pump beta subunits.

We developed two signature patterns for beta 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.

-Consensus pattern: [FYWMV]-x(2)-[FYWM]-x-[FYW]-[DN]-x(6)-[LIVMF]-[GA]-R-T-
                    x(3)-[WRL]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.

-Consensus pattern: [RK]-x(2)-C-[RKQWI]-x(5)-L-x(2)-C-[SA]-G
                    [The 2 C's are involved in disulfide bonds]
-Sequences known to belong to this class detected by the pattern: ALL,  except
 for the beta subunit of the  sodium pump  of  brine shrimp  whose sequence is
 highly divergent in that region.
-Other sequence(s) detected in Swiss-Prot: NONE.

-Last update: December 2004 / Pattern and text revised.

[ 1] Horisberger J.D., Lemas V., Kraehenbuhl J.P., Rossier B.C.
     "Structure-function relationship of Na,K-ATPase."
     Annu. Rev. Physiol. 53:565-584(1991).
     PubMed=1645948; DOI=10.1146/annurev.ph.53.030191.003025
[ 2] McDonough A.A., Geering K., Farley R.A.
     "The sodium pump needs its beta subunit."
     FASEB J. 4:1598-1605(1990).
     PubMed=2156741
[ 3] 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.
     "The 60- to 90-kDa parietal cell autoantigen associated with
     autoimmune gastritis is a beta subunit of the gastric H+/K(+)-ATPase
     (proton pump)."
     Proc. Natl. Acad. Sci. U.S.A. 87:6418-6422(1990).
     PubMed=1974721

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