Cloning and characterization of CXIP1, a novel PICOT domain-containing Arabidopsis protein that associates with CAX1

J Biol Chem. 2003 Feb 21;278(8):6503-9. doi: 10.1074/jbc.M210883200. Epub 2002 Dec 11.


Regulation of Ca(2+) transporters is a vital component of signaling. The Arabidopsis H(+)/Ca(2+) exchanger CAX1 contains an N-terminal autoinhibitory domain that prevents Ca(2+) transport when CAX1 is heterologously expressed in yeast. Using a yeast screen, we have identified three different proteins that activate CAX1. One of these, CXIP1 (CAX-interacting protein-1; 19.3 kDa) has amino acid similarity to the C terminus of PICOT (protein kinase C-interacting cousin of thioredoxin) proteins. Although PICOT proteins are found in a variety of organisms, a function has not been previously ascribed to a plant PICOT protein. We demonstrate that CXIP1 activated the CAX1 homolog CAX4, but not CAX2 or CAX3. An Arabidopsis homolog of CXIP1 (CXIP2) weakly activated CAX4, but not CAX1. In a yeast two-hybrid assay, CXIP1 interacted with the N terminus of CAX1. In competition analysis, CXIP1 and a CAX1 N-terminal peptide appeared to bind to similar N-terminal domains of CAX1. Chimeric CAX3 constructs containing the N terminus of CAX1 were activated by CXIP1. In Arabidopsis, CXIP1 transcripts, like CAX1, accumulated in response to different metal conditions. This work thus characterizes a new class of signaling molecules in plants that may regulate CAX transporters in vivo.

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
  • Antiporters / metabolism*
  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / chemistry
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Binding Sites
  • Calcium-Binding Proteins / metabolism*
  • Carrier Proteins / chemistry
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cation Transport Proteins*
  • Cloning, Molecular
  • Conserved Sequence
  • Kinetics
  • Molecular Sequence Data
  • Protein Binding
  • Saccharomyces cerevisiae / genetics
  • Sequence Alignment
  • Sequence Homology, Amino Acid


  • Antiporters
  • Arabidopsis Proteins
  • CXIP1 protein, Arabidopsis
  • Calcium-Binding Proteins
  • Carrier Proteins
  • Cation Transport Proteins
  • calcium-hydrogen antiporters

Associated data

  • GENBANK/AY157988
  • GENBANK/AY157989
  • GENBANK/AY163162