ATP dependence of anion uptake by isolated vacuoles: requirement for excess Mg2+.
Vacuoles were isolated from barley mesophyll protoplasts. [14C]Malate or 36Cl- were taken up from the surrounding medium. Uptake was only slightly increased in the presence of equimolar levels of ATP and Mg2+ (as magnesium gluconate). In the presence of excess Mg2+ in the medium, ATP-stimulated uptake of malate and chloride increased several-fold. Stimulation by excess Mg2+ was not observed for ATP-stimulated amino acid uptake by isolated vacuoles. Stimulation of uptake by excess Mg2+ was observed at all malate concentrations upto 10 mmol.l-1. The content of Mg2+ needed for half-maximum stimulation was about 3.5 mmol.l-1 in the presence of 1 mmol.l-1 ATP. The increase in Mg2+ concentration had no effect on the tonoplast ATPase activity.
Dietz
K J
KJ
Institut für Botanik und Pharmazeutische Biologie, Julius-Maximilians-Universität Würzburg, F.R.G.
Lang
M
M
Schönrock
M
M
Zink
C
C
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism*; D001692:Biological Transport; D001467:Hordeum; D006868:Hydrolysis; D008274:Magnesium / Q000378:metabolism*; D008293:Malates / Q000378:metabolism; D011523:Protoplasts / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism*
D008293:Malates; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D008274:Magnesium