title: Regulation of CAX1, an Arabidopsis Ca(2+)/H+ antiporter. Identification of an N-terminal autoinhibitory domain.
abstract: Regulation of Ca(2+) transport determines the duration of a Ca(2+) signal, and hence, the nature of the biological response. Ca(2+)/H+ antiporters such as CAX1 (cation exchanger 1), play a key role in determining cytosolic Ca(2+) levels. Analysis of a full-length CAX1 clone suggested that the CAX1 open reading frame contains an additional 36 amino acids at the N terminus that were not found in the original clone identified by suppression of yeast (Saccharomyces cerevisiae) vacuolar Ca(2+) transport mutants. The long CAX1 (lCAX1) could not suppress the yeast Ca(2+) transport defects despite localization to the yeast vacuole. Calmodulin could not stimulate lCAX1 Ca(2+)/H+ transport in yeast; however, minor alterations in the 36-amino acid region restored Ca(2+)/H+ transport. Sequence analysis suggests that a 36-amino acid N-terminal regulatory domain may be present in all Arabidopsis CAX-like genes. Together, these results suggest a structural feature involved in regulation of Ca(2+)/H+ antiport.
authors.affiliation: Plant Physiology Group, U.S. Department of Agriculture/Agricultural Research Service, Baylor College of Medicine, 1100 Bates Street, Houston, TX 77030, USA.
authors.forename: J K
authors.initials: JK
authors.lastname: Pittman
authors.forename: K D
authors.initials: KD
authors.lastname: Hirschi
mesh_terms: D000595:Amino Acid Sequence; D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins; D002874:Chromosome Mapping; D003600:Cytosol / Q000378:metabolism; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014617:Vacuoles / Q000378:metabolism
chemical_list: D017920:Antiporters; D029681:Arabidopsis Proteins; D002135:Calcium-Binding Proteins; D027682:Cation Transport Proteins; C027614:calcium-hydrogen antiporters; D006859:Hydrogen; D002118:Calcium