The NhaB Na+/H+ antiporter is essential for intracellular pH regulation under alkaline conditions in Escherichia coli

J Biochem. 1994 Aug;116(2):285-90. doi: 10.1093/oxfordjournals.jbchem.a124521.

Abstract

We isolated a mutant of Escherichia coli which was defective in an Na+/H+ antiporter and grew poorly under alkaline conditions [Ishikawa, T., Hama, H., Tsuda, T., and Tsuchiya, T. (1987) J. Biol. Chem. 262, 7443-7446]. Later, it was concluded that the defective Na+/H+ antiporter in the mutant was the NhaB system, and the nhaB gene was mapped to 25.6 min on the E. coli chromosome [Thelen, P., Tsuchiya, T., and Goldberg, E.B. (1991) J. Bacteriol. 173, 6553-6557]. We found that the NhaB-defective cells cannot grow in a high pH medium. Furthermore, intracellular pH in the mutant cells was almost the same as extracellular pH between 7.9 and 9.1, that is, intracellular pH was not regulated at this pH range. On the other hand, intracellular pH of the wild-type cells was maintained at about 7.6 when the extracellular pH was between 7.6 and 8.5. Thus, the NhaB Na+/H+ antiporter is essential for the regulation of intracellular pH under alkaline conditions in E. coli. Introduction of nhaA gene into the mutant cells increased Na+/H+ antiporter activity, but did not restore the defective growth and defective intracellular pH regulation under alkaline conditions.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / physiology*
  • Escherichia coli / genetics
  • Escherichia coli / growth & development
  • Escherichia coli / physiology*
  • Hydrogen-Ion Concentration
  • Intracellular Fluid / metabolism
  • Mutation
  • Sodium-Hydrogen Exchangers / genetics
  • Sodium-Hydrogen Exchangers / physiology*

Substances

  • Bacterial Proteins
  • Sodium-Hydrogen Exchangers