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- Title
Characterization of CXIP4, a novel Arabidopsis protein that activates the H<sup>+</sup>/Ca<sup>2+</sup> antiporter, CAX1
- Authors
Cheng, Ning-Hui; Liu, Jian-Zhong; Nelson, Richard S.; Hirschi, Kendal D.
- Abstract
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 <F><UNL TYPE="BAR" STYLE="S">C</UNL></F>A<F><UNL TYPE="BAR" STYLE="S">X i</UNL></F>nteracting <F><UNL TYPE="BAR" STYLE="S">p</UNL></F>rotein 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.
- Subjects
CALCIUM ions; CELLULAR signal transduction; ARABIDOPSIS; CALCIUM-binding proteins
- Publication
FEBS Letters, 2004, Vol 559, Issue 1-3, p99
- ISSN
0014-5793
- Publication type
Article
- DOI
10.1016/S0014-5793(04)00036-5