title: CAX1, an H+/Ca2+ antiporter from Arabidopsis.
abstract: Reestablishment of the resting state after stimulus-coupled elevations of cytosolic-free Ca2+ requires the rapid removal of Ca2+ from the cytosol of plant cells. Here we describe the isolation of two genes, CAX1 and CAX2, from Arabidopsis thaliana that suppress a mutant of Saccharomyces cerevisiae that has a defect in vacuolar Ca2+ accumulation. Both genes encode polypeptides showing sequence similarities to microbial H+/Ca2+ antiporters. Experiments on vacuolar membrane-enriched vesicles isolated from yeast expressing CAX1 or CAX2 demonstrate that these genes encode high efficiency and low efficiency H+/Ca2+ exchangers, respectively. The properties of the CAX1 gene product indicate that it is the high capacity transporter responsible for maintaining low cytosolic-free Ca2+ concentrations in plant cells by catalyzing pH gradient-energized vacuolar Ca2+ accumulation.
authors.affiliation: Whitehead Institute for Biomedical Research, Nine Cambridge Center, MA 02142, USA.
authors.forename: K D
authors.initials: KD
authors.lastname: Hirschi
authors.forename: R G
authors.initials: RG
authors.lastname: Zhen
authors.forename: K W
authors.initials: KW
authors.lastname: Cunningham
authors.forename: P A
authors.initials: PA
authors.lastname: Rea
authors.forename: G R
authors.initials: GR
authors.lastname: Fink
mesh_terms: D000595:Amino Acid Sequence; D017920:Antiporters / Q000235:genetics*; D017360:Arabidopsis / Q000235:genetics*; D001483:Base Sequence; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics*; D027682:Cation Transport Proteins; D002474:Cell-Free System; D017931:DNA Primers / Q000737:chemistry; D018076:DNA, Complementary / Q000235:genetics; D017343:Genes, Plant; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics*; D011994:Recombinant Proteins; D012441:Saccharomyces cerevisiae; D017386:Sequence Homology, Amino Acid; D012995:Solubility; D014170:Transformation, Genetic; D014617:Vacuoles / Q000737:chemistry / Q000378:metabolism
chemical_list: D017920:Antiporters; D002135:Calcium-Binding Proteins; D027682:Cation Transport Proteins; D017931:DNA Primers; D018076:DNA, Complementary; D010940:Plant Proteins; D011994:Recombinant Proteins; C027614:calcium-hydrogen antiporters; D002118:Calcium