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Related Experiment Videos

(Na/ + K+)ATPase has one functioning phosphorylation site per alpha subunit.

W H Peters, H G Swarts, J J de Pont

    Nature
    |March 26, 1981
    PubMed
    Summary

    This study investigated the phosphorylation mechanism of sodium-potassium adenosine triphosphatase ((Na+ + K+)ATPase). Findings show both alpha subunits can be phosphorylated simultaneously, refuting the half-of-the-sites mechanism.

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    The Journal of biological chemistry·2001

    Area of Science:

    • Biochemistry
    • Molecular Biology
    • Enzymology

    Background:

    • Sodium-potassium adenosine triphosphatase ((Na+ + K+)ATPase) is a crucial membrane protein involved in ion transport.
    • The enzyme comprises catalytic (alpha) and beta subunits, with the alpha subunit's phosphorylation mechanism being a subject of study.
    • Previous research suggested a 'half-of-the-sites' mechanism for alpha subunit phosphorylation.

    Purpose of the Study:

    • To investigate the phosphorylation capacity of the (Na+ + K+)ATPase alpha subunits.
    • To determine if both alpha subunits within the enzyme molecule can be phosphorylated concurrently.
    • To provide evidence to either support or refute the proposed 'half-of-the-sites' mechanism.

    Main Methods:

    • Enzyme purification and characterization.

    Related Experiment Videos

  • Determination of protein concentration using Lowry assay.
  • Measurement of ATP, ouabain, and vanadate binding capacities.
  • Phosphorylation assays using ATP and inorganic phosphate.
  • Calculation of molar binding and phosphorylation capacities based on enzyme molecular weight.

    • Main Results:

    • The enzyme exhibits maximal binding and phosphorylation capacities of 3.5--4.3 nmol P per mg protein.
    • A molar binding and phosphorylation capacity of 0.87--1.07 mol per mol enzyme was derived.
    • Evidence was presented indicating that every alpha subunit can be phosphorylated simultaneously.

    Conclusions:

    • The simultaneous phosphorylation of all alpha subunits contradicts the 'half-of-the-sites' mechanism.
    • (Na+ + K+)ATPase phosphorylation likely involves all available alpha subunits.
    • This finding clarifies the catalytic mechanism of (Na+ + K+)ATPase.