CLONING AND SEQUENCING OF AN NA+ H+ ANTIPORTER GENE FROM THE MARINE BACTERIUM VIBRIO-ALGINOLYTICUS/

A gene has been cloned from a DNA library from the marine bacterium Vi brio alginolyticus that functionally complements a mutant strain of Es cherichia coli, NM81, defective in an Na+/H+ antiporter (NhaA). The cl oned Vibrio gene restored NM81 to grow in a medium containing 0.5 M Na Cl at pH 7.5 and concomitantly led to an increase in Na+/H+ antiport a ctivity. The nucleotide sequence of the cloned fragment revealed an op en reading frame, which encodes a protein with a predicted 383 amino a cid sequence and molecular mass of 40 400 Da. The hydropathy profile i s characteristic of a membrane protein with 11 membrane spanning regio ns. The deduced amino acid sequence is 58% identical with E coli NhaA.