Repression of Proton extrusion from Intact Cucumber Roots and the Proton Transport Rate of Microsomal Membrane Vesicles of the Roots due to Ca2+ Starvation |
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Authors: | Matsumoto Hideaki |
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Affiliation: | Institute for Agricultural and Biological Sciences, Okayama University Chuo 2-20-1, Kurashiki, Okayama 710, Japan |
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Abstract: | Proton extrusion from cucumber roots decreased markedly duringCa2+ starvation in the presence of KC1. Vesicles with ATP-dependentproton transport activity were prepared from the microsomalmembrane fraction of control and Ca2+-starved roots. The protontransport rate of the vesicles from Ca2+-starved roots was repressedto less than half of the vesicles prepared from the controlroots. K+-Mg2+-ATPase activity associated with the vesiclesprepared from Ca2+-starved roots was approximately one-thirdof the activity associated with those prepared from controlroots. Km values of the proton transport rate and K+-Mg2+-ATPasefor ATP were much higher in vesicles prepared from Ca2+-starvedroots. The repression of proton extrusion linked with K+ uptake inthe Ca2+-starved roots could be largely caused by the reducedproton pumping activity associated with microsomal membranesin the roots. (Received May 25, 1987; Accepted October 14, 1987) |
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