Arabidopsis thaliana and Saccharomyces cerevisiae NHX1 genes encode amiloride sensitive electroneutral Na+/H+ exchangers

Biochem J. 2000 Oct 1;351(Pt 1):241-9. doi: 10.1042/0264-6021:3510241.

Abstract

Sodium at high millimolar levels in the cytoplasm is toxic to plant and yeast cells. Sequestration of Na(+) ions into the vacuole is one mechanism to confer Na(+)-tolerance on these organisms. In the present study we provide direct evidence that the Arabidopsis thaliana At-NHX1 gene and the yeast NHX1 gene encode low-affinity electroneutral Na(+)/H(+) exchangers. We took advantage of the ability of heterologously expressed At-NHX1 to functionally complement the yeast nhx1-null mutant. Experiments on vacuolar vesicles isolated from yeast expressing At-NHX1 or NHX1 provided direct evidence for pH-gradient-energized Na(+) accumulation into the vacuole. A major difference between NHX1 and At-NHX1 is the presence of a cleavable N-terminal signal peptide (SP) in the former gene. Fusion of the SP to At-NHX1 resulted in an increase in the magnitude of Na(+)/H(+) exchange, indicating a role for the SP in protein targeting or regulation. Another distinguishing feature between the plant and yeast antiporters is their sensitivity to the diuretic compound amiloride. Whereas At-NHX1 was completely inhibited by amiloride, NHX1 activity was reduced by only 20-40%. These results show that yeast as a heterologous expression system provides a convenient model to analyse structural and regulatory features of plant Na(+)/H(+) antiporters.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amiloride / metabolism
  • Amiloride / pharmacology*
  • Arabidopsis / genetics*
  • Arabidopsis / metabolism
  • Arabidopsis Proteins*
  • Carrier Proteins / chemistry
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cation Transport Proteins*
  • Cinnamates*
  • Cloning, Molecular
  • Conserved Sequence
  • Diuretics / metabolism
  • Diuretics / pharmacology*
  • Fungal Proteins / chemistry
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism
  • Gene Deletion
  • Genetic Complementation Test
  • Hydrogen / metabolism
  • Hydrogen-Ion Concentration
  • Hygromycin B / analogs & derivatives
  • Hygromycin B / pharmacology
  • Inhibitory Concentration 50
  • Intracellular Membranes / drug effects
  • Intracellular Membranes / metabolism
  • Ion Transport / drug effects
  • Phenotype
  • Plant Proteins / chemistry
  • Plant Proteins / genetics
  • Plant Proteins / metabolism
  • Protein Binding
  • Protein Sorting Signals / physiology
  • Protein Structure, Tertiary
  • Saccharomyces cerevisiae / cytology
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins*
  • Salts / pharmacology
  • Sodium / metabolism
  • Sodium / pharmacology
  • Sodium-Hydrogen Exchangers / chemistry
  • Sodium-Hydrogen Exchangers / genetics
  • Sodium-Hydrogen Exchangers / metabolism*
  • Vacuoles / drug effects
  • Vacuoles / metabolism

Substances

  • Arabidopsis Proteins
  • Carrier Proteins
  • Cation Transport Proteins
  • Cinnamates
  • Diuretics
  • Fungal Proteins
  • NHX1 protein, Arabidopsis
  • NHX1 protein, S cerevisiae
  • Plant Proteins
  • Protein Sorting Signals
  • Saccharomyces cerevisiae Proteins
  • Salts
  • Sodium-Hydrogen Exchangers
  • Hygromycin B
  • hygromycin A
  • Amiloride
  • Hydrogen
  • Sodium