Distinct N-Terminal Regulatory Domains of Ca²⁺/H⁺ Antiporters

• Published in: Plant physiology (Bethesda) Vol. 130; no. 2; pp. 1054 - 1062
• Main Authors: Pittman, Jon K., Coimbatore S. Sreevidya, Shigaki, Toshiro, Hanayo Ueoka-Nakanishi, Hirschi, Kendal D.
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01.10.2002; American Society of Plant Physiologists
• Subjects: Absorption. Translocation of ions and substances. Permeability; Agronomy. Soil science and plant productions; Amino acids; Antiporters; Biological and medical sciences; Cell Biology and Signal Transduction; Cell physiology; Economic plant physiology; Fundamental and applied biological sciences. Psychology; Gene expression regulation; Nutrition. Photosynthesis. Respiration. Metabolism; Open reading frames; Phenotypes; Plant cells; Plant physiology and development; Plants; Plasma membrane and permeation; Protein isoforms; Proteins; Yeasts; Membrane protein; Calcium; Cell permeability; Interspecific comparison; Vigna radiata; Ionic channel; Arabidopsis thaliana; Grain legume; Leguminosae; Cruciferae; Dicotyledones; Angiospermae; N terminal-Sequence; Proton; Regulatory sequence; Spermatophyta; Experimental plant; Molecular domain; Carrier protein; Aminoacid sequence
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.008193

The regulation of intracellular Ca2+ levels is achieved in part by high-capacity vacuolar Ca2+/H+ antiporters. An N-terminal regulatory region (NRR) on the Arabidopsis Ca2+/H+ antiporter CAX1 (cation exchanger 1) has been shown previously to regulate Ca2+ transport by a mechanism of N-terminal auto-inhibition. Here, we examine the regulation of other CAX transporters, both within Arabidopsis and from another plant, mung bean (Vigna radiata), to ascertain if this mechanism is commonly used among Ca2+/H+ antiporters. Biochemical analysis of mung bean VCAX1 expressed in yeast (Saccharomyces cerevisiae) showed that N-terminal truncated VCAX1 had approximately 70% greater antiport activity compared with full-length VCAX1. A synthetic peptide corresponding to the NRR of CAX1, which can strongly inhibit Ca2+ transport by CAX1, could not dramatically inhibit Ca2+ transport by truncated VCAX1. The N terminus of Arabidopsis CAX3 was also shown to contain an NRR. Additions of either the CAX3 or VCAX1 regulatory regions to the N terminus of an N-terminal truncated CAX1 failed to inhibit CAX1 activity. When fused to N-terminal truncated CAX1, both the CAX3 and VCAX1 regulatory regions could only auto-inhibit CAX1 after mutagenesis of specific amino acids within this NRR region. These findings demonstrate that N-terminal regulation is present in other plant CAX transporters, and suggest distinct regulatory features among these transporters.