Transmembrane segment M3 is essential to thapsigargin sensitivity of the sarcoplasmic reticulum Ca2+-ATPase

Five different chimeric fusion proteins between the sarcoplasmic reticulum Ca2+-ATPase and the rat kidney al isoform of the Na+,K+-ATPase were expressed in COS-1 cells and analyzed functionally. In two chimeras, the only Na+,K+-ATPase-derived part consisted of the region corresponding to the third t...

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Bibliographic Details
Published in:The Journal of biological chemistry 1994-10, Vol.269 (43)
Main Authors: Norregaard, A. (University of Aarhus, Aarhus C, Denmark.), Vilsen, B, Andersen, J.P
Format: Article
Language:English
Subjects:
ADENOSINA TRIFOSFATASA
ADENOSINE TRIPHOSPHATASE
ADN
CALCIO
CALCIUM
CATION
CATIONES
CHIMERE
COMPOSICION QUIMICA
COMPOSITION CHIMIQUE
CONEJO (ORYCTOLAGUS)
INHIBICION
INHIBITION
LACTONAS
LACTONE
LAPIN (ORYCTOLAGUS)
QUIMERA
RETICULO
RETICULUM
SESQUITERPENOIDE
SESQUITERPENOS
UMBELLIFERAE
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Summary:Five different chimeric fusion proteins between the sarcoplasmic reticulum Ca2+-ATPase and the rat kidney al isoform of the Na+,K+-ATPase were expressed in COS-1 cells and analyzed functionally. In two chimeras, the only Na+,K+-ATPase-derived part consisted of the region corresponding to the third transmembrane segment. These proteins phosphorylated from ATP in the presence of a high Ca2+ concentration and from Pi in the absence of Ca2+, but the phosphorylation displayed strongly reduced sensitivity to inhibition by thapsigargin. In two other chimeras, the N-terminal two-thirds of the molecule were derived from Na+,K+-ATPase, except the region containing the fourth transmembrane segment. These proteins were unable to phosphorylate from ATP but phosphorylated from Pi, the latter reaction being insensitive to inhibition by thapsigargin. In the last chimera, the N-terminal two-thirds of the molecule were derived from Na+,K+-ATPase, except the region corresponding to both the third and the fourth transmembrane segments. This chimera phosphorylated from Pi in a reaction that was fully sensitive to inhibition by thapsigargin. It can be concluded that the third transmembrane segment is indispensable to thapsigargin sensitivity of the Ca2+-ATPase and most likely, therefore, constitutes a major binding region for thapsigargin
ISSN:0021-9258
1083-351X