The ATP‐driven Na⁺‐pump in the plasma membrane of the marine unicellular alga, Platymonas viridis

Abstract

The ATP-supported =NA' uptake by plasma membrane vesicles from the marine microalga, PZatymonas viridis, was studied. At pH 7 in the medium, Na' uptake did not occur in the presence of ATP although dpH across the plasma membrane was generated, The ATP-dependent Na* uptake was induced by adding the protonophore, CICCP. At pH 8, Na' uptake took place when ATP was added even without ClCcP. The ApH generated across the plasma membrane was negligible under these conditions. The Na+ uptake at pH 8 was not affected by ClCCP and amiloride, an inhibitor of the Na+/H' antiporter. It is concluded that the ATP-supported Na+ uptake by PI. viridis vesicles is catalyzed by Na+-ATPase.

The Na + -translocating ATPase in the plasma membrane of the marine microalga Tetraselmis viridis catalyzes Na + /H + exchange

“…Detection of Na + uptake Sodium uptake by the PM vesicles was monitored by a tracer technique using 22 Na + , as described earlier (Balnokin and Popova 1994). The standard 0.5-ml assay medium contained 0.5 M mannitol, 20 mM BTP-Hepes (pH 7.8), 1 mM MgSO 4 , 1 mM EGTA, and approx.…”

“…Highly purified PM vesicles were prepared according to the method described earlier (Balnokin et al 1993) with some minor modifications (Balnokin et al 1997). Briefly, the method includes the following key steps: (i) moderate treatment of the cells with trypsin which led to partial destruction of the glycoprotein cell wall; (ii) exposure of the trypsin-treated cells to a mild hypo-osmotic shock which results in cytoplasm outflow and formation of large cytoplasmic drops enveloped by PM; (iii) purification of the PMs by differential centrifugation and centrifugation in a discontinuous sucrose gradient.…”

“…During the last decade, Na + -ATPases were found to operate in the plasma membrane (PM) of two marine algal species, Tetraselmis (Platymonas) viridis Rouch. (Balnokin and Popova 1994;Balnokin et al 1997) and Heterosigma akashiwo (Wada et al 1989;Shono et al 1996). Na + -ATPases are of particular interest as the Na + -transporters fulfilling primary active Na + translocation across the PM.…”

Functional expression of an animal type-Na+-ATPase gene from a marine red seaweed Porphyra yezoensis increases salinity tolerance in rice plants

“…Although Na + -ATPase activity has been detected in the plasma membranes of marine unicellular algae Heterosigma akashiwo, Platynomas viridis and Dunaliella parva (Balnokin and Popova 1994;Gimmler et al 1989;Shono et al 1995;Shono et al 1996), the identification of a gene from H. akashiwo encoding an Na + -ATPase with high homology to animal-type Na + /K + -ATPases was unexpected (Shono et al 2001), indicating the unexpected importance of animal-type Na + /K + -ATPases in adaptation of marine algae to high salinity environments (Gimmler 2000).…”

Halotolerant Cyanobacterium Aphanothece halophytica Contains an Na+-dependent F1F0-ATP Synthase with a Potential Role in Salt-stress Tolerance

“…To date, two types of Na ϩ -transporting mechanisms are known to extrude Na ϩ from the cytoplasm. The Na ϩ /H ϩ antiporters are of one type that utilize energy of the transmembrane proton gradient for Na ϩ translocation (4), whereas another type is the primary ATP-driven Na ϩ -pumps in the plasma membrane (P-type Na ϩ -ATPase) (5,6). The P-type Na ϩ -ATPase is a single component polypeptide found in many organisms, including yeast.…”