title: Molecular properties of a novel, hydrophilic cation-binding protein associated with the plasma membrane.
abstract: A new type of protein was found in Arabidopsis thaliana, PCaP1, which is rich in glutamate and lysine residues. The protein bound (45)Ca(2+) even in the presence of a high concentration of Mg(2+). Real-time polymerase chain reaction and histochemical analysis of promoter-beta-glucuronidase fusions revealed that PCaP1 was expressed in most organs. The PCaP1 protein was detected immunochemically in these organs. Treatment of Arabidopsis seedlings with Cu(2+), sorbitol, or flagellin oligopeptide enhanced the transcription. On the other hand, other sugars, abscisic acid, gibberellic acid, dehydration, and low temperature had little or no effect on PCaP1 transcript abundance. The transient expression of PCaP1 fused to green fluorescent protein in Arabidopsis cells and the subcellular fractionation of tissue homogenate showed that PCaP1 protein is localized to the plasma membrane, although PCaP1 has no predicted transmembrane domain. PCaP1 was associated with the plasma membrane under natural conditions and was released from the membrane at high concentrations of Ca(2+) or Mg(2+) in vitro. These results suggest that the hydrophilic protein PCaP1 binds Ca(2+) and other cations and is stably associated with the plasma membrane.
authors.affiliation: Laboratory of Cell Dynamics, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Ide
authors.forename: Nahoko
authors.initials: N
authors.lastname: Nagasaki
authors.forename: Rie
authors.initials: R
authors.lastname: Tomioka
authors.forename: Momoe
authors.initials: M
authors.lastname: Suito
authors.forename: Takehiro
authors.initials: T
authors.lastname: Kamiya
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Maeshima
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D002412:Cations / Q000737:chemistry*; D002462:Cell Membrane / Q000378:metabolism*; D035264:Flowers / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000378:metabolism; D018517:Plant Roots / Q000166:cytology / Q000378:metabolism; D018520:Plant Shoots / Q000378:metabolism; D018547:Plant Stems / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D002412:Cations; C521040:PCaP1 protein, Arabidopsis