Picomolar concentrations of tentoxin affect Mg2+- and Ca2+-ATPase activities of plasma membrane vesicles from roots of winter wheat seedlings |
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Authors: | Martin G Klotz Alajos Bérczi László Erdei Bernd Liebermann |
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Institution: | Sektion Biologie der Fried-rich-Schiller-Univ., Neugasse 23, Jena, DDR-6900, GDR;Inst. of Biophysics, Biological Research Center, Hungarian Academy Sciences, POB 521, H-6701 Szeged, Hungary. |
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Abstract: | Purified plasmalemma vesicles were isolated in the presence of 250 m M sucrose from roots of 14-day-old seedlings of winter wheat ( Triticum aestivum L. Martonvásári-8) by phase partitioning of salt-washed microsomal fractions in a Dextran-polyethylene glycol two-phase system, and both Mg2+- and Ca2+-ATPase activities were detected. Orthovanadate-sensitive Mg2+-ATPase activity associated with the inside of right side-out plasmalemma (PM) vesicles (latency 98%) was inhibited 76% by 0.3 m M Ca2+, Ca2+-dependent ATPase activity located partly on the inside and partly on the outside of plasmalemma vesicles (latency 47%) was not affected by Mg2+. Mg2+-ATPase activity was inhibited by 68% and inhibition of Mg2+ activation by 0.3 m M Ca2+ partly disappeared in the presence of 10 p M tentoxin, a fungal phytotoxin. Mg2+-ATPase activity remained inhibited up to 10 n M tentoxin while at 1 μ M tentoxin Mg2+ activation was as high as without tentoxin. K+-stimulation and vanadate inhibition was increased and decreased, respectively, by 100 p M -10 n M tentoxin. Ca2+-dependent ATPase activity was continuously increased by 1 p M -10 n M tentoxin, but at 1 μ M tentoxin the stimulation disappeared. The effects of p M tentoxin on plasma-lemma Mg2+-ATPase are discussed in relation to its influence on K+ transport in wheat seedlings. |
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Keywords: | Calcium-ATPase magnesium-ATPase plasmalemma roots tentoxin Triticum aestivum wheat |
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