Genetic defect of the sodium pump-defective mutant Nap-1 from the marine Vibrio alginolyticus.

The marine bacterium, Vibrio alginolyticus, has a respiratory chain-linked Na(+)-translocating NADH-quinone reductase (NQR). Among several mutant cells defective in Na+ pump activity, Nap1 was a very stable mutant and a spontaneous revertant could not be isolated from Nap1. Using genetic information from the recently sequenced nqr operon, the genetic defects in Nap1 were examined, and the sodium pump-defective mutant Nap1 was found to be caused by the insertion of a 1.2 kbp DNA fragment into the C-terminal region of nqr6 gene.