Mechanism of N-terminal autoinhibition in the Arabidopsis Ca(2+)/H(+) antiporter CAX1

J Biol Chem. 2002 Jul 19;277(29):26452-9. doi: 10.1074/jbc.M202563200. Epub 2002 May 10.


Regulation of Ca(2+)/H(+) antiporters may be an important function in determining the duration and amplitude of cytosolic Ca(2+) oscillations. Previously the Arabidopsis Ca(2+)/H(+) transporter, CAX1 (cation exchanger 1), was identified by its ability to suppress yeast mutants defective in vacuolar Ca(2+) transport. Recently, a 36-amino acid N-terminal regulatory region on CAX1 has been identified that inhibits CAX1-mediated Ca(2+)/H(+) antiport. Here we show that a synthetic peptide designed against the CAX1 36 amino acids inhibited Ca(2+)/H(+) transport mediated by an N-terminal-truncated CAX1 but did not inhibit Ca(2+) transport by other Ca(2+)/H(+) antiporters. Ca(2+)/H(+) antiport activity measured from vacuolar-enriched membranes of Arabidopsis root was also inhibited by the CAX1 peptide. Through analyzing CAX chimeric constructs the region of interaction of the N-terminal regulatory region was mapped to include 7 amino acids (residues 56-62) within CAX1. The CAX1 N-terminal regulatory region was shown to physically interact with this 7-amino acid region by yeast two-hybrid analysis. Mutagenesis of amino acids within the N-terminal regulatory region implicated several residues as being essential for regulation. These findings describe a unique mode of antiporter autoinhibition and demonstrate the first detailed mechanisms for the regulation of a Ca(2+)/H(+) antiporter from any organism.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Antiporters / metabolism
  • Antiporters / physiology*
  • Arabidopsis
  • Calcium / metabolism
  • Calcium-Binding Proteins / metabolism
  • Calcium-Binding Proteins / physiology*
  • Cation Transport Proteins*
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Peptide Mapping
  • Protein Structure, Secondary
  • Recombinant Fusion Proteins / metabolism
  • Serine / metabolism
  • Structure-Activity Relationship
  • Threonine / metabolism


  • Antiporters
  • Calcium-Binding Proteins
  • Cation Transport Proteins
  • Recombinant Fusion Proteins
  • calcium-hydrogen antiporters
  • Threonine
  • Serine
  • Calcium