title: Effects of Mg2+ and ATP on the phosphate transporter of sarcoplasmic reticulum.
abstract: The extra uptake of Ca2+ by vesicles of sarcoplasmic reticulum (SR) observed in the presence of Pi, attributable to transport of Pi by the Pi-transporter, has been studied. It has been shown that the Pi transporter is stimulated by ATP. Single channel conductance measurements have shown that the Cl- channel in the SR membrane is impermeable to Pi. It is suggested that the transporter could be an ion antiporter system. Studies of uptake as a function of pH and Mg2+ concentration suggest that transport of MgHPO4 and H2PO-4 are faster than transport of HPO2-4. For oxalate and pyrophosphate, Mg2+ binding inhibits transport. It is suggested that protonation of lysine residue(s) at the anion binding site increase the rate of transport.
authors.affiliation: Department of Biochemistry, University of Southampton, U.K.
authors.forename: H I
authors.initials: HI
authors.lastname: Stefanova
authors.forename: S D
authors.initials: SD
authors.lastname: Jane
authors.forename: J M
authors.initials: JM
authors.lastname: East
authors.forename: A G
authors.initials: AG
authors.lastname: Lee
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D018118:Chloride Channels; D006863:Hydrogen-Ion Concentration; D008051:Lipid Bilayers; D008274:Magnesium / Q000494:pharmacology*; D008565:Membrane Proteins / Q000187:drug effects / Q000378:metabolism*; D010070:Oxalates / Q000378:metabolism*; D019815:Oxalic Acid; D028044:Phosphate-Binding Proteins; D010710:Phosphates / Q000378:metabolism*; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D018118:Chloride Channels; D008051:Lipid Bilayers; D008565:Membrane Proteins; D010070:Oxalates; D028044:Phosphate-Binding Proteins; D010710:Phosphates; D000255:Adenosine Triphosphate; D019815:Oxalic Acid; D008274:Magnesium; D002118:Calcium