Comparisons of Plasma Membranes from Shoots and Roots of Winter Rye (Secale cereale L. cv. Puma): Polypeptide Composition, ATPase Activity and Specific Naphthylphthalamic Acid Binding Capacity

Polypeptide compositions, ATPase characteristics, and the N-1-naphthylphthalamicacid binding capacity of plasma membranes prepared from winterrye (Secale cereale L. cv. Puma) shoots and roots were examinedand compared. Some unique polypeptides were revealed in each plasma membraneby one- and two-dimensional slab gel electrophoresis. A differencewas also detected in glycopeptide compositions. The plasma membranesfrom both organs contained Mg²⁺-stimulated ATPase exhibitingslightly different properties in the divalent cation specificityand the kinetic constants. The ATPase activities from both organsshowed a similar optimum pH around 6.5, simple Michaelis-Mentensaturation with increasing ATP-Mg concentrations, and littleK⁺-stimulation at the optimum pH. Both ATPases were inhibitedby orthovanadate, however, the degree of inhibition was a littledifferent in each membrane sample. The specific N-1-naphthylphthalamicacid binding capacity in the shoot plasma membrane was 2.6-foldhigher than that in the root plasma membrane. These results suggest that polypeptide compositions of plasmamembranes vary corresponding with a difference in the physiologicalfunctions of plasma membranes between shoots and roots of winterrye. ¹ Contribution No. 2670 from the Institute of Low TemperatureScience. (Received May 17, 1984; Accepted October 9, 1984)