NADH-Linked Electron Transfer Induces Cd^<2+> Movement in Corn Root Plasma Membrane Vesicles

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The rate of electron transfer from NADH to ferricya-nide associated with corn root plasma membrane vesicles was not significantly affected by the presence of Ca^<2+> Cd^<2+>, Zn^<2+>, or Co^<2+>. However unlike Ca^<2+> other tested divalent cations induced an electron transfer-dependent increase in light scattering by the vesicles. The efficacy in inducing the light scattering increase followed the order of Cd^<2+> > Zn^<2+> > Co^<2+>. The extent of the light scattering change increased as the concentration of added Cd^<2+> in-creased. Using phase contrast microscopy, the increase in light scattering was related to an expansion of the vesicles. Accompanying the volume increase, a decrease of Cd^<2+> concentration in the external space was observed by the use of Arsenazo III, a nretallochromophore specific for diva-lent cations. Under a specified electron transfer condition, a similar percentage of decrease over a wide range of initial Cd^<2+> concentration was detected. The presence of A_23187 decreased the rate and extent of light scattering increase and its associated Cd^<2+> concentration change. However, A_23187 had no effect on scattering changes already established by the electron transfer and Cd^<2+>. These results suggest that the NADH linked electron transfer reaction may induce a Cd^<2+> uptake by the vesicles of corn root plasma membrane with inside-out orientation.
日本植物生理学会の論文