Repression of proton extrusion from intact cucumber roots and the proton transport rate of microsomal membrane vesicles of the roots due to Ca2+ starvation

Matsumoto, H.

Plant and Cell Physiology 29(1): 79-84


ISSN/ISBN: 0032-0781
Accession: 001673045

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Proton extrusion decreased markedly during Ca2+ starvation in the presence of KCl. Vesicles with ATP-dependent proton transport activity were prepared from the microsomal membrane fraction of control and Ca2+ -starved roots. The proton transport rate of the vesicles from Ca2+-starved roots was repressed to less than half that of the vesicles prepared from the control roots. K+-Mg2+-ATPase activity associated with the vesicles prepared from Ca2+-starved roots was approximately one-third of the activity associated with those prepared from control roots. Km values of the proton transport rate and K+-Mg2+-ATPase for ATP were much higher in vesicles prepared from Ca2+-starved roots. It is suggested that the repression of proton extrusion linked with K+ uptake in the Ca2+-starved roots could be largely caused by the reduced proton pumping activity associated with microsomal membranes in the roots.