Functional Analysis OF NhaP Type Na⁺/H⁺ Antiporter from a Halotolerant A. halophytica

Abstract

We are working on the Na⁺/H⁺ antiporters from plants and cyanobacteria. Recently, we showed that a cyanobacterium Synechocystis sp. PCC 6803 contains an Na⁺/H⁺ antiporter, SynNhaP1, homologous to eucaryotic (SOS1 from Arabidopsis) and procaryotic (NhaP from Pseudomonas aeruginosa) ones, but not to the E. coli NhaA, NhaB and ChaA (Plant Physiol., 125, 437-446 (2000)). We also isolated NhaP type Na⁺/H⁺ antiporter (ApNhaP1) from a halotolerant cyanobacterium A. halophytica (J. Biol. Chem 276, 36931-36938 (2001)). ApNhaP1 exhibited the Na⁺/H⁺ antiporter activity over a wide range of pH between 5 and 9 as is the case of SynNhaP1, but exhibited a different ion specificity. Overexpression of ApNhaP1 in a fleshwater cyanobacterium Synechococcus PCC 7942 confers the salt tolerance of freshwater cyanobacterium capable of growth in sea water. These results will be presented.