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ARS Home » Plains Area » Houston, Texas » Children's Nutrition Research Center » Research » Publications at this Location » Publication #165964
Title: CHARACTERIZATION OF CXIP4, A NOVEL ARABIDOPSIS PROTEIN THAT ACTIVATES THE H+/CA2+ ANTIPORTER, CAX1

Author
item CHENG, NING-HUI - BAYLOR COLL MEDICINE
item LIU, JIAN-ZHONG - SAM ROBERTS NOBLE FOUND
item NELSON, RICHARD - SAM ROBERTS NOBLE FOUND
item Hirschi, Kendal

Submitted to: The Federation of European Biochemical Societies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2004
Publication Date: 1/26/2004
Citation: Cheng, N., Liu, J., Nelson, R.S., Hirschi, K. 2004. Characterization of CXIP4, a novel Arabidopsis protein that activates the H+/Ca2+ antiporter, CAX1. The Federation of European Biochemical Societies. 559(1):99-106.

Interpretive Summary: In order to manipulate plant growth and nutrient content, we must assign biological function to an array of plant genes. Here we characterize a new gene which appears to function in plant nutrient uptake. We can now begin to manipulate this gene to dissect its role in plant nutrition.

Technical 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 vacuoloar Ca2+ transporter mutants due to an N-terminal autoinhibition mechanism that prevents Ca2+ trnasport. Using a yeast screen, we have identified CAX interacting protein 4 (CXIP4) that activated full-length CAX1, but not full-length CAX2, CAX3 or CAX4. CXIP4 enclodes 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.