Molecular properties of a novel, hydrophilic cation-binding protein associated with the plasma membrane

• Published in: Journal of experimental botany 2007-01, Vol.58 (5), p.1173-1183
• Main Authors: Ide, Yuki, Nagasaki, Nahoko, Tomioka, Rie, Suito, Momoe, Kamiya, Takehiro, Maeshima, Masayoshi
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Antibodies; Arabidopsis - cytology; Arabidopsis - metabolism; Arabidopsis Proteins - chemistry; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; Biological and medical sciences; calcium; Calcium-Binding Proteins; Carrier Proteins; cation; Cations - chemistry; Cell Membrane - metabolism; Cell membranes; Cell physiology; Chemical suspensions; Cytosol; Flowers - metabolism; Fluorescence; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant - physiology; membrane-associated protein; Messenger RNA; Metal ions; Molecular Sequence Data; myristoylation; Plant Leaves - metabolism; Plant physiology and development; Plant Roots - cytology; Plant Roots - metabolism; Plant Shoots - metabolism; Plant Stems - metabolism; Plants; plasma membrane; Plasma membrane and permeation; Polymerase chain reaction; Proteins; Research Papers
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/erl284

A new type of protein was found in Arabidopsis thaliana, PCaP1, which is rich in glutamate and lysine residues. The protein bound 45Ca2+ even in the presence of a high concentration of Mg2+. Real-time polymerase chain reaction and histochemical analysis of promoter–β-glucuronidase fusions revealed that PCaP1 was expressed in most organs. The PCaP1 protein was detected immunochemically in these organs. Treatment of Arabidopsis seedlings with Cu2+, 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 Ca2+ or Mg2+ in vitro. These results suggest that the hydrophilic protein PCaP1 binds Ca2+ and other cations and is stably associated with the plasma membrane.