Na+-ATPases of halotolerant microalgae

Na+ homeostasis in the cytoplasm is a common property of all organisms, irrespective of their taxonomic position. Low Na+ concentrations in the cytoplasm of living cells are maintained by specialized Na+-transporting molecular machines operating in the cell membranes. In eukaryotic cells, Na+-transporting ATPases of P-type play the important role in keeping the Na+ homeostasis. This review summarizes the authors' investigations demonstrating the operation of the Na+-transporting P-type ATPases in the plasma membrane of green marine microalgae. Experiments described here provided the first evidence for the existence of the primary Na+-pump in plasma membranes of organisms attributed to the plant kingdom. The significance of the Na+-ATPases in halotolerant microalgae Dunaliella maritima and Tetraselmis viridis inhabiting saline environments is discussed.