Characterization of Arabidopsis Ca2+/H+ exchanger CAX3

Biochemistry. 2011 Jul 19;50(28):6189-95. doi: 10.1021/bi2003839. Epub 2011 Jun 22.


Plant calcium (Ca(2+)) gradients, millimolar levels in the vacuole and micromolar levels in the cytoplasm, are regulated in part by high-capacity vacuolar cation/H(+) exchangers (CAXs). Several CAX transporters, including CAX1, appear to contain an approximately 40-amino acid N-terminal regulatory region (NRR) that modulates transport through N-terminal autoinhibition. Deletion of the NRR from several CAXs (sCAX) enhances function in plant and yeast expression assays; however, to date, there are no functional assays for CAX3 (or sCAX3), which is 77% identical and 91% similar in sequence to CAX1. In this report, we create a series of truncations in the CAX3 NRR and demonstrate activation of CAX3 in both yeast and plants by truncating a large portion (up to 90 amino acids) of the NRR. Experiments with endomembrane-enriched vesicles isolated from yeast expressing activated CAX3 demonstrate that the gene encodes Ca(2+)/H(+) exchange with properties distinct from those of CAX1. The phenotypes produced by activated CAX3-expressing in transgenic tobacco lines are also distinct from those produced by sCAX1-expressing plants. These studies demonstrate shared and unique aspects of CAX1 and CAX3 transport and regulation.

Publication types

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

MeSH terms

  • Antiporters / chemistry*
  • Antiporters / genetics
  • Arabidopsis / chemistry*
  • Arabidopsis / genetics
  • Arabidopsis Proteins / chemistry*
  • Arabidopsis Proteins / genetics
  • Biological Transport / genetics
  • Calcium / chemistry*
  • Cation Transport Proteins / chemistry
  • Cation Transport Proteins / genetics
  • Hydrogen / chemistry*
  • Peptide Fragments / chemistry
  • Peptide Fragments / genetics
  • Saccharomyces cerevisiae / genetics
  • Tobacco / genetics


  • Antiporters
  • Arabidopsis Proteins
  • CAX3 protein, Arabidopsis
  • Cation Transport Proteins
  • Peptide Fragments
  • calcium-hydrogen antiporters
  • Hydrogen
  • Calcium