Linked Life Data

7891030

Source:http://linkedlifedata.com/resource/pubmed/id/7891030

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
Pt 1
pubmed:dateCreated
1995-4-17
pubmed:abstractText
We have reviewed the structural and functional role of the beta-subunit in a subfamily of the P-ATPases known as the alpha/beta-heterodimeric, cation-exchange ATPases. The subfamily consists of the various isoforms of Na+/K(+)-ATPase and H+/K(+)-ATPase, both of which pump a cation out of the cell (Na+ or H+, respectively) in recycle exchange for K+. Much of the earlier work has emphasized the functional activities of the alpha-subunit, which shares many characteristics with the broader P-ATPase family. It is now clear that the glycosylated beta-subunit is an essential component of the cation-exchange ATPase subfamily. All beta-subunit isoforms have three highly conserved disulfide bonds within the extracellular domain that serve to stabilize the alpha-subunit, alpha/beta interaction and functional activity of the holoenzyme. Evidence strongly suggests that the beta-subunit is involved in the K(+)-dependent reactions of the enzymes, such as the E1-E2 transition and K+ occlusion, and that the extracellular domain of the beta-subunit plays an important role in determining the kinetics of K+ interaction. In most vertebrate cells, the unassociated alpha-subunit is restricted to the endoplasmic reticulum (ER), and assembly of the alpha/beta complex occurs within the ER. Signals for exiting the ER and directing the correct intracellular trafficking are primarily determined by the beta-subunit; Na+/K(+)-ATPase typically terminates in the plasma membrane facing the basolateral membrane, whereas all isoforms of H+/K(+)-ATPase terminate in the apical membrane. The C-terminal extracellular domain of the beta-subunit is important for proper interaction with the alpha-subunit and for correct intracellular trafficking. Oligosaccharides on the beta-subunit are not essential for enzyme function, but do serve to enhance the efficiency of alpha/beta association by increasing the lifetime of the unassociated beta-subunit and the stability of the alpha/beta complex to tryptic attack. We propose that highly specialized glycosylation on the beta-subunit of the gastric H+/K(+)-ATPase may help to protect that enzyme from the harsh extracellular environment of the stomach.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0022-0949
pubmed:author
pubmed:issnType
Print
pubmed:volume
198
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1-17
pubmed:dateRevised
2007-11-15
pubmed:meshHeading
pubmed:year
1995
pubmed:articleTitle
Functional significance of the beta-subunit for heterodimeric P-type ATPases.
pubmed:affiliation
Department of Molecular and Cell Biology, University of California, Berkeley 94720.
pubmed:publicationType
Journal Article, Review