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Plausible Stoichiometry of the Interacting Nucleotide-Binding Sites in the Ca2+-ATPase from Sarcoplasmic Reticulum Membranes
- Source :
- Archives of Biochemistry and Biophysics. 368:298-302
- Publication Year :
- 1999
- Publisher :
- Elsevier BV, 1999.
-
Abstract
- The Ca 2+ ,Mg 2+ -ATPase from sarcoplasmic reticulum couples ATP hydrolysis to Ca 2+ transport toward the lumen of the muscular vesicular system. Combined structural and functional studies suggest that the Ca 2+ binding sites are formed by six amino acids of the same polypeptide and that cation translocation may take place through a channel inside a monomer of the ATPase. However, calorimetric, fluorescent, and kinetic studies suggest that the ATPase may assemble into functional oligomers of as yet unknown stoichiometry. We have addressed this question and attempted to determine the ATPase stoichiometry using a biophysical approach based on the analysis of the ATPase inhibition by fluorescein 5′-isothiocyanate in the presence of increasing ATP concentrations. For native SR membranes, our inhibition data are well described by a model consisting of two interacting nucleotide-binding sites per oligomer. This stoichiometry was disrupted in detergent C 12 E 8 -solubilized ATPase. Thus, these findings suggest that interacting nucleotide binding sites of the ATPase may appear as dimers, and imply that interactions of the globular cytoplasmic domains would play a modulatory role of the protein enzymatic activity.
- Subjects :
- ATPase
Biophysics
Calcium-Transporting ATPases
Biochemistry
Oligomer
chemistry.chemical_compound
ATP hydrolysis
Animals
Binding site
Muscle, Skeletal
Molecular Biology
chemistry.chemical_classification
Binding Sites
biology
Nucleotides
Endoplasmic reticulum
Intracellular Membranes
Amino acid
Calcium ATPase
Sarcoplasmic Reticulum
Membrane
chemistry
biology.protein
Rabbits
Protein Binding
Subjects
Details
- ISSN :
- 00039861
- Volume :
- 368
- Database :
- OpenAIRE
- Journal :
- Archives of Biochemistry and Biophysics
- Accession number :
- edsair.doi.dedup.....3a215be415a0e5ba21d7a9e4736837f6