Characterization of CXIP4, a novel Arabidopsis protein that activates the H+/Ca2+ antiporter, CAX1

FEBS Lett. 2004 Feb 13;559(1-3):99-106. doi: 10.1016/S0014-5793(04)00036-5.


Precise regulation of calcium transporters is essential for modulating the Ca2+ signaling network that is involved in the growth and adaptation of all organisms. The Arabidopsis H+/Ca2+ antiporter, CAX1, is a high capacity and low affinity Ca2+ transporter and several CAX1-like transporters are found in Arabidopsis. When heterologously expressed in yeast, CAX1 is unable to suppress the Ca2+ hypersensitivity of yeast vacuolar Ca2+ transporter mutants due to an N-terminal autoinhibition mechanism that prevents Ca2+ transport. Using a yeast screen, we have identified CAX nteracting Protein 4 (CXIP4) that activated full-length CAX1, but not full-length CAX2, CAX3 or CAX4. CXIP4 encodes a novel plant protein with no bacterial, fungal, animal, or mammalian homologs. Expression of a GFP-CXIP4 fusion in yeast and plant cells suggests that CXIP4 is targeted predominantly to the nucleus. Using a yeast growth assay, CXIP4 activated a chimeric CAX construct that contained specific portions of the N-terminus of CAX1. Together with other recent studies, these results suggest that CAX1 is regulated by several signaling molecules that converge on the N-terminus of CAX1 to regulate H+/Ca2+ antiport.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / physiology*
  • Carrier Proteins / genetics
  • Carrier Proteins / physiology*
  • Cell Nucleus / chemistry
  • Green Fluorescent Proteins
  • Luminescent Proteins / genetics
  • Nuclear Proteins
  • Plant Leaves / cytology
  • Plant Leaves / ultrastructure
  • Recombinant Fusion Proteins / genetics
  • Sequence Alignment
  • Tobacco / cytology
  • Tobacco / ultrastructure
  • Yeasts / genetics


  • Arabidopsis Proteins
  • CXIP4 protein, Arabidopsis
  • Carrier Proteins
  • Luminescent Proteins
  • Nuclear Proteins
  • Recombinant Fusion Proteins
  • Green Fluorescent Proteins