Na⁺/K⁺-ATPase a Primary Membrane Transporter: An Overview and Recent Advances with Special Reference to Algae

The maintenance of ionic homeostasis in the cytoplasm is an essential and crucial physiological process for all living beings. At cellular level, Na⁺ concentrations are maintained by specialized Na⁺ transporting molecular machines, which operate in the cell or plasma membrane. In eukaryotes Na⁺ transporting P-type ATPase play an important role in Na⁺ homeostasis that is known as Na⁺/K⁺-ATPase in animal cells in which K⁺ acts as a counter ion for the exchange of sodium. Na⁺/K⁺-ATPase is not found in plants. In plants and fungi, proton gradients are maintained by plasma membrane H⁺-ATPase while in animal cells Na⁺ and K⁺ gradient is maintained by Na⁺/K⁺-ATPase. However, in case of algae, a few reports of Na⁺/K⁺-ATPase are available, that maintains optimum concentration gradients in the cytoplasm and is used by Na⁺/H⁺ antiporter to exchange of Na⁺ and H⁺ ions. The membrane potential derived as a result of ion gradients across the membrane is base for a variety of cellular processes. An active Na⁺ dependent cycle (P-type ATPase) is scarcely reported in algae as compared to marine bacteria/cyanobacteria and animals. The characterization of these transporter gene-encoding membrane transports in seaweed would contribute to the understanding of abiotic stress tolerance in these organisms. This review highlights the detailed account of algal along with animal type Na⁺-ATPase i.e. occurrence, properties, significance and their recent progress.