EFFECTS OF H-ATPASE ACTIVITIES ON CD2+ MOVEMENT INDUCED BY NADH-LINKED ELECTRON-TRANSFER IN ROOT PLASMA-MEMBRANE VESICLES()

The vanadate-sensitive H+-ATPase activities, proton pumping and ATP hy drolysis of the corn root plasma membrane vesicles were not significan tly affected by the electron transfer from NADH to ferricyanide. Simil arly, the electron transfer activity was also not affected by activati on of the H+-ATPase. These results suggested a lack of direct interact ion between the two energy-yielding processes in the plasma membrane. The NADH-linked electron transfer induced a Cd2+ concentration-depende nt increase in the light scattering of the membrane vesicles. The incr ease was previously determined to be an indication of Cd2+ uptake by t he vesicles (Tu et al., 1996). The rate of the light scattering increa se was significantly decreased when the ATPase was activated by the ad dition of Mg-ATP. Neither free ATP nor free Mg2+ had the inhibitory ef fect on the light scattering change. The inhibition of the light scatt ering increase associated with the activation of the ATPase exhibited a pH dependence and vanadate sensitivity similar to those of the ATPas e activities. The results suggest that the ATPase activities could reg ulate the Cd2+ movement activated by the NADH-linked electron transfer .