Characterization of cytosolic cyclophilin from guard cells of Vicia faba L.
The effect of immunosuppressant cyclosporin A (CsA) on inward-rectifying K(+)-channels and biochemical analysis have indicated the presence of cyclophilin in guard cells of Vicia faba. In this study, we identified a full-length cDNA sequence, vcCyP, encoding cyclophilin (CyP), a peptidyl-prolyl cis-trans isomerase of guard cell protoplasts (GCPs) from Vicia faba L. The deduced amino acid sequence revealed that vcCyP contained 171 amino acid residues and exhibited a strong similarity to previously described cytosolic CyP isoforms from other plants. vcCyP had seven extra amino acid residues, which is a characteristic of the cytosolic form of plant CyPs. A complex of recombinant vcCyP and CsA inhibited the phosphatase activity of bovine calcineurin, a type 2B protein phosphatase, with a half-inhibitory concentration of 0.2 microM. Protein phosphatase activity was measured in the cytosolic fraction of GCPs using a 32P-labeled myelin basic protein (32P-MBP) and the activity was increased by a physiological concentration of Ca2+ (1 microM). This Ca(2+)-stimulated phosphatase activity was inhibited by CsA, suggesting the presence of both cytosolic CyP and calcineurin-like protein phosphatase in guard cells. Northern blot analysis showed that the transcription level of vcCyP was much higher in GCPs than in root and leaf tissues of Vicia.
Kinoshita
T
T
Department of Biology, Faculty of Science, Kyushu University, Fukuoka, Japan.
Shimazaki
K
K
D001483:Base Sequence; D065095:Calcineurin Inhibitors; D016572:Cyclosporine; D003600:Cytosol / Q000737:chemistry*; D018076:DNA, Complementary / Q000235:genetics; D007887:Fabaceae / Q000737:chemistry* / Q000166:cytology; D008969:Molecular Sequence Data; D019696:Peptidylprolyl Isomerase / Q000235:genetics / Q000302:isolation & purification*; D018515:Plant Leaves / Q000737:chemistry* / Q000166:cytology; D010940:Plant Proteins / Q000235:genetics / Q000302:isolation & purification; D010946:Plants, Medicinal; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D020033:Protein Isoforms / Q000235:genetics / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D014018:Tissue Distribution
D065095:Calcineurin Inhibitors; D018076:DNA, Complementary; D010940:Plant Proteins; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D020033:Protein Isoforms; D016572:Cyclosporine; D019696:Peptidylprolyl Isomerase