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Kinetics of ATP-dependent Mg2+ flux in mitochondria

E Kun

    Biochemistry
    |June 1, 1976
    PubMed

    Insights

    Mitochondria accumulate magnesium ions (Mg2+) via ATP. Lysosomes interfere with this process, but digitonin treatment removes them, revealing Mg2+ flux depends solely on ATP, Mg2+, and substrates.

    Area of Science:

    • Mitochondrial Physiology
    • Ion Transport
    • Cellular Biochemistry

    Background:

    • Mitochondria actively accumulate magnesium ions (Mg2+) in a process dependent on adenosine triphosphate (ATP).
    • Lysosomal contamination in mitochondrial preparations can significantly alter the observed Mg2+ uptake kinetics.
    • Understanding Mg2+ flux is crucial for mitochondrial function and cellular homeostasis.

    Purpose of the Study:

    • To elucidate the precise factors governing ATP-dependent Mg2+ accumulation in isolated mitochondria.
    • To investigate the role of lysosomes in modulating mitochondrial Mg2+ transport.
    • To develop a kinetic model for Mg2+ flux across the mitochondrial inner membrane.

    Main Methods:

    • Isolated mitochondria were treated with digitonin to selectively remove lysosomes.
    • Mg2+ uptake and efflux were measured using various concentrations of ATP, Mg2+, and specific inhibitors.
    • Kinetic analysis was performed to derive rate constants and develop a transport model.

    Main Results:

    • Digitonin treatment removed lysosomal interference, allowing accurate assessment of Mg2+ flux.
    • In purified mitochondria, Mg2+ flux depended only on ATP, Mg2+ concentration, and electron transport substrates.
    • Inhibitors like oligomycin, atractyloside, and ruthenium red demonstrated specific effects on Mg2+ transport, while uncouplers induced efflux.

    Conclusions:

    • Lysosomes significantly influence mitochondrial Mg2+ accumulation, necessitating their removal for accurate studies.
    • Mitochondrial Mg2+ flux is a complex, bi-directional process regulated by ATP, Mg2+, and the electron transport system.
    • A kinetic model accurately describes Mg2+ movement in digitonin-treated mitoplasts.

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