Functional comparisons between isoforms of the sarcoplasmic or endoplasmic reticulum family of calcium pumps

ATP-dependent calcium pumps that reside in intracellular organelles are encoded by a family of structurally related enzymes, termed the sarcoplasmic or endoplasmic reticulum Ca(2+)-ATPases (SERCA), which each have a distinct pattern of tissue-specific and developmentally regulated expression. A COS-...

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Bibliographic Details
Published in:The Journal of biological chemistry 1992-07, Vol.267 (20), p.14483-14489
Main Authors: LYTTON, J, WESTLIN, M, BURK, S. E, SHULL, G. E, MACLENNAN, D. H
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - metabolism
Analytical, structural and metabolic biochemistry
Animals
Biological and medical sciences
calcium
Calcium - metabolism
Calcium - pharmacology
Calcium-Transporting ATPases - genetics
Calcium-Transporting ATPases - metabolism
Cell Line
endoplasmic reticulum
Endoplasmic Reticulum - enzymology
Enzymes and enzyme inhibitors
Fundamental and applied biological sciences. Psychology
Gene Expression
Hydrolases
Isoenzymes - genetics
Isoenzymes - metabolism
Kinetics
Mathematics
Phosphorylation
pumps
sarcoplasmic reticulum
Sarcoplasmic Reticulum - enzymology
Transfection
Vanadates - pharmacology
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Summary:ATP-dependent calcium pumps that reside in intracellular organelles are encoded by a family of structurally related enzymes, termed the sarcoplasmic or endoplasmic reticulum Ca(2+)-ATPases (SERCA), which each have a distinct pattern of tissue-specific and developmentally regulated expression. A COS-1 cell expression system was used to examine the biochemical properties of the isoforms: SERCA1 (fast-twitch skeletal muscle). SERCA2a (cardiac/slow-twitch skeletal muscle), SERCA2b (ubiquitous smooth- and non-muscle), and SERCA3 (non-muscle). Each isoform was expressed efficiently and appeared to be targeted to the endoplasmic reticulum. All isoforms displayed qualitatively similar enzymatic properties and were activated by calcium in a cooperative manner with a Hill coefficient of 2. The quantitative properties of SERCA1 and SERCA2a (the muscle isoforms) were identical in all respects. SERCA2b, however, appeared to have a lower turnover rate for both calcium transport and ATP hydrolysis. SERCA3 displayed a reduced apparent affinity for calcium, an increased apparent affinity for vanadate, and an altered pH dependence when compared with the other isoforms. These properties are consistent with an enzyme in which the equilibrium between the E1 and E2 conformations is shifted toward the E2 state.
ISSN:0021-9258
1083-351X
DOI:10.1016/s0021-9258(19)49738-x