Betam, a structural member of the X,K-ATPase beta subunit family, resides in the ER and does not associate with any known X,K-ATPase alpha subunit

Details

Serval ID
serval:BIB_B75AAC599E4A
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Betam, a structural member of the X,K-ATPase beta subunit family, resides in the ER and does not associate with any known X,K-ATPase alpha subunit
Journal
Biochemistry
Author(s)
Crambert  G., Beguin  P., Pestov  N. B., Modyanov  N. N., Geering  K.
ISSN
0006-2960 (Print)
Publication state
Published
Issued date
05/2002
Volume
41
Number
21
Pages
6723-33
Notes
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S. --- Old month value: May 28
Abstract
betam, a muscle-specific protein, is structurally closely related to the X,K-ATPase beta subunits, but its intrinsic function is not known. In this study, we have expressed betam in Xenopus oocytes and have investigated its biosynthesis and processing as well as its putative role as a chaperone of X,K-ATPase alpha subunits, as a regulator of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA), or as a Ca(2+)-sensing protein. Our results show that betam is stably expressed in the endoplasmic reticulum (ER) in its core glycosylated, partially trimmed form. Both full-length betam, initiated at Met(1), and short betam species, initiated at Met(89), are detected in in vitro translations as well as in Xenopus oocytes. betam cannot associate with and stabilize Na,K-ATPase (NK), or gastric and nongastric H,K-ATPase (HK) alpha isoforms. betam neither assembles stably with SERCA nor is its trypsin sensitivity or electrophoretic mobility influenced by Ca(2+). A mutant, in which the distinctive Glu-rich regions in the betam N-terminus are deleted, remains stably expressed in the ER and can associate with, but not stabilize X,K-ATPase alpha subunits. On the other hand, a chimera in which the ectodomain of betam is replaced with that of beta1 NK associates efficiently with alpha NK isoforms and produces functional Na,K-pumps at the plasma membrane. In conclusion, our results indicate that betam exhibits a cellular location and functional role clearly distinct from the typical X,K-ATPase beta subunits.
Keywords
Adenosine Triphosphatases/biosynthesis/chemistry/*metabolism Animals Calcium/*metabolism Calcium-Transporting ATPases/*metabolism Chimerin Proteins/metabolism Endoplasmic Reticulum/*metabolism Glycoproteins/metabolism Glycosylation H(+)-K(+)-Exchanging ATPase/chemistry Humans *Membrane Glycoproteins Molecular Chaperones/metabolism Muscle, Skeletal Na(+)-K(+)-Exchanging ATPase/chemistry Oocytes/metabolism Protein Subunits Sarcoplasmic Reticulum Calcium-Transporting ATPases Structure-Activity Relationship Swine Tissue Distribution Xenopus laevis
Pubmed
Web of science
Create date
24/01/2008 12:28
Last modification date
20/08/2019 15:25
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