Electrogenesis in Plasma Membrane Fraction of Halotolerant Microalga Dunaliella maritima and Effects of N,N′-Dicyclohexylcarbodiimide

The effects of N,N '-dicyclohexylcarbodiimide (DCCD), non-specific inhibitor of various transport systems functioning in biological membranes, on Na+-transporting P-type ATPase of the green halotolerant microalga Dunaliella maritima were studied in the experiments with vesicular plasma membranes isolated from the alga cells. The effects of DCCD on electrogenic/ion transport function of the enzyme and its ATP hydrolase activity were investigated. Electrogenic/ion transport function of the enzyme was recorded as a Na+-dependent generation of electric potential on the vesicle membranes with the help of the potential-sensitive probe oxonol VI. It was found that unlike many other ion-transporting ATPases, the Na+-ATPase of D. maritimais insensitive to DCCD. This agent did not inhibit either ATP hydrolysis catalyzed by this enzyme or its transport activity. At the same time DCCD affected the ability of the vesicle membranes to maintain electric potential generated by theD. maritima Na+-ATPase. The observed effects can be explained based on the assumption that DCCD interacts with the Na+/H+ antiporter in the plasma membrane of D. maritima.