Evidence of differential pH regulation of the Arabidopsis vacuolar Ca2+/H+ antiporters CAX1 and CAX2

FEBS Lett. 2005 May 9;579(12):2648-56. doi: 10.1016/j.febslet.2005.03.085. Epub 2005 Apr 9.


The Arabidopsis Ca(2+)/H(+) antiporters cation exchanger (CAX) 1 and 2 utilise an electrochemical gradient to transport Ca(2+) into the vacuole to help mediate Ca(2+) homeostasis. Previous whole plant studies indicate that activity of Ca(2+)/H(+) antiporters is regulated by pH. However, the pH regulation of individual Ca(2+)/H(+) antiporters has not been examined. To determine whether CAX1 and CAX2 activity is affected by pH, Ca(2+)/H(+) antiport activity was measured in vacuolar membrane vesicles isolated from yeast heterologously expressing either transporter. Ca(2+) transport by CAX1 and CAX2 was regulated by cytosolic pH and each transporter had a distinct cytosolic pH profile. Screening of CAX1/CAX2 chimeras identified an amino acid domain within CAX2 that altered the pH-dependent Ca(2+) transport profile so that it was almost identical to the pH profile of CAX1. Results from mutagenesis of a specific His residue within this domain suggests a role for this residue in pH regulation.

Publication types

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

MeSH terms

  • Antiporters / chemistry*
  • Antiporters / genetics
  • Antiporters / metabolism*
  • Arabidopsis / chemistry*
  • Arabidopsis Proteins / chemistry
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Biological Transport
  • Calcium / metabolism*
  • Cytosol / chemistry
  • Histidine / chemistry
  • Hydrogen / metabolism*
  • Hydrogen-Ion Concentration
  • Mutagenesis, Site-Directed
  • Protein Structure, Tertiary
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Saccharomyces cerevisiae / chemistry
  • Saccharomyces cerevisiae / genetics
  • Vacuoles / metabolism


  • Antiporters
  • Arabidopsis Proteins
  • Recombinant Proteins
  • Histidine
  • Hydrogen
  • Calcium