title: Coupling Ratio for Ca(2+) Transport by Calcium Oxalate Precipitation.
abstract: The SERCA isoform 1a is constructed to transport 2 Ca(2+) ions across the sarcoplasmic reticulum membrane coupled to the hydrolysis of one molecule of MgATP. However, observed coupling ratios for Ca(2+) transported/ATP hydrolzyed are usually less than 2:1, since part of the Ca(2+) accumulated at high intravesicular concentrations by the active transport of Ca(2+) leaks out of the vesicles because of Ca(2+)-induced Ca(2+) exchange. However, in the presence of a high concentration of oxalate (5 mM) Ca(2+) will precipitate as Ca-oxalate inside the vesicles and thereby be prevented from leaking out and, in addition, this treatment will reduce the intravesicular free concentration of Ca(2+) to a level where optimal coupling ratios of 2:1 can be achieved.
authors.affiliation: Department of Biomedicine, Aarhus University, Aarhus C, Denmark.|Centre for Membrane Pumps in Cells and Disease, Danish National Research Foundation, Aarhus C, Denmark.
authors.forename: Pankaj
authors.initials: P
authors.lastname: Sehgal
authors.affiliation: Department of Molecular Biology and Genetics, Aarhus University, Aarhus C, Denmark.|Centre for Membrane Pumps in Cells and Disease, Danish National Research Foundation, Aarhus C, Denmark.
authors.forename: Claus
authors.initials: C
authors.lastname: Olesen
authors.affiliation: Department of Biomedicine, Aarhus University, Aarhus C, Denmark. jvm@biomed.au.dk.|Centre for Membrane Pumps in Cells and Disease, Danish National Research Foundation, Aarhus C, Denmark. jvm@biomed.au.dk.
authors.forename: Jesper V
authors.initials: JV
authors.lastname: Møller
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000737:chemistry*; D002129:Calcium Oxalate / Q000737:chemistry; D020013:Calcium Signaling; D006868:Hydrolysis; D012519:Sarcoplasmic Reticulum / Q000737:chemistry / Q000201:enzymology; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000737:chemistry* / Q000378:metabolism
chemical_list: D002129:Calcium Oxalate; D000255:Adenosine Triphosphate; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D002118:Calcium
keywords: Calcium ATPase; Calcium accumulation; Calcium transport; Oxalate; SERCA; Sarcoplasmic reticulum vesicles