| Functional approach to the catalytic site of the sarcoplasmic reticulum Ca(2+)-ATPase: binding and hydrolysis of ATP in the absence of Ca(2+). | |
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MedLine Citation:
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PMID: 15337857 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Isolated sarcoplasmic reticulum vesicles in the presence of Mg(2+) and absence of Ca(2+) retain significant ATP hydrolytic activity that can be attributed to the Ca(2+)-ATPase protein. At neutral pH and the presence of 5 mM Mg(2+), the dependence of the hydrolysis rate on a linear ATP concentration scale can be fitted by a single hyperbolic function. MgATP hydrolysis is inhibited by either free Mg(2+) or free ATP. The rate of ATP hydrolysis is not perturbed by vanadate, whereas the rate of p-nitrophenyl phosphate hydrolysis is not altered by a nonhydrolyzable ATP analog. ATP binding affinity at neutral pH and in a Ca(2+)-free medium is increased by Mg(2+) but decreased by vanadate when Mg(2+) is present. It is suggested that MgATP hydrolysis in the absence of Ca(2+) requires some optimal adjustment of the enzyme cytoplasmic domains. The Ca(2+)-independent activity is operative at basal levels of cytoplasmic Ca(2+) or when the Ca(2+) binding transition is impeded. |
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Authors:
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Antonio Lax; Fernando Soler; Francisco Fernández-Belda |
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Publication Detail:
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Type: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Journal of bioenergetics and biomembranes Volume: 36 ISSN: 0145-479X ISO Abbreviation: J. Bioenerg. Biomembr. Publication Date: 2004 Jun |
Date Detail:
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Created Date: 2004-08-31 Completed Date: 2005-03-07 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 7701859 Medline TA: J Bioenerg Biomembr Country: United States |
Other Details:
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Languages: eng Pagination: 265-73 Citation Subset: IM |
Affiliation:
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Departamento de Bioquímica y Biología Molecular A, Facultad de Veterinaria, Universidad de Murcia, Campus de Espinardo, 30071 Murcia, Spain. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Adenosine Triphosphate
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metabolism* Animals Calcium-Transporting ATPases / metabolism* Catalysis Female Hydrolysis Magnesium / metabolism Models, Molecular Muscle, Skeletal / metabolism* Phosphorus Radioisotopes Protein Binding Rabbits Sarcoplasmic Reticulum / metabolism* Vanadates / metabolism |
| Chemical | |
Reg. No./Substance:
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0/Phosphorus Radioisotopes; 0/Vanadates; 56-65-5/Adenosine Triphosphate; 7439-95-4/Magnesium; EC 3.6.1.8/Calcium-Transporting ATPases |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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