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Phosphorylation of the Adenosine Triphosphatase in a Deoxycholate-Treated Plasma Membrane Fraction from Corn Roots

Donald P. Briskin and Robert T. Leonard
Plant Physiology
Vol. 70, No. 5 (Nov., 1982), pp. 1459-1464
Stable URL: http://www.jstor.org/stable/4267712
Page Count: 6
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Phosphorylation of the Adenosine Triphosphatase in a Deoxycholate-Treated Plasma Membrane Fraction from Corn Roots
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Abstract

The ATP phosphohydrolase (ATPase) activity of a corn (Zea mays L., WF9 × Mo17) root plasma membrane fraction was enriched almost 2-fold by selective extraction with 0.1% (w/v) deoxycholate. The detergent treatment solubilized about 30% of the total membrane protein and some ATP hydrolyzing activity that was not K+-stimulated, but the major portion of the ATPase activity could be pelleted with membranes. The properties of the ATPase associated with the detergent-extracted plasma membrane fraction were similar to those for the ATPase of the untreated plasma membrane fraction with respect to substrate specificity, pH optimum, kinetics with MgATP, ion stimulation, and inhibitor sensitivity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed only minor differences in protein composition resulting from the detergent treatment. The plasma membrane fraction from corn roots contained an endogenous protein kinase activity. This was shown by the time course of phosphate incorporation and by the labeling of a number of protein bands on SDS-polyacrylamide gel electrophoresis. The deoxycholate treatment removed measurable protein kinase activity and allowed the demonstration of a rapidly turning over covalent phosphorylated intermediate associated with the detergent-extracted plasma membrane fraction. The phosphorylated intermediate was present as a 100,000 dalton polypeptide and may represent the catalytic subunit of the plasma membrane K+-ATPase.

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