Journal
PLANTA
Volume 219, Issue 2, Pages 332-337Publisher
SPRINGER-VERLAG
DOI: 10.1007/s00425-004-1224-7
Keywords
marine alga; Na+-ATPase; Na+/H+ exchanger; salt tolerance; Tetraselmis
Categories
Ask authors/readers for more resources
Our previous investigations have established that Na+ translocation across the Tetraselmis viridis plasma membrane (PM) mediated by the primary ATP-driven Na+-pump, Na+-ATPase, is accompanied by H+ counter-transport [Y.V. Balnokin et al. (1999) FEBS Lett 462:402-406]. The hypothesis that the Na+-ATPase of T. viridis operates as an Na+/H+ exchanger is tested in the present work. The study of Na+ and H+ transport in PM vesicles isolated from T. viridis demonstrated that the membrane-permeant anion NO3- caused (i) an increase in ATP-driven Na+ uptake by the vesicles, (ii) an increase in (Na++ATP)-dependent vesicle lumen alkalization resulting from H+ efflux out of the vesicles and (iii) dissipation of electrical potential, Deltapsi, generated across the vesicle membrane by the Na+-ATPase. The (Na++ATP)-dependent lumen alkalization was not significantly affected by valinomycin, addition of which in the presence of K+ abolished Deltapsi at the vesicle membrane. The fact that the Na+-ATPase-mediated alkalization of the vesicle lumen is sustained in the absence of the transmembrane Deltapsi is consistent with a primary role of the Na+-ATPase in driving H+ outside the vesicles. The findings allowed us to conclude that the Na+-ATPase of T. viridis directly performs an exchange of Na+ for H+. Since the Na+-ATPase generates electric potential across the vesicle membrane, the transport stoichiometry is mNa(+)/nH(+), where m>n.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available