Journal Article

Characterization of Cytosolic Cyclophilin from Guard Cells of <i>Vicia faba</i> L

Toshinori Kinoshita and Ken-ichiro Shimazaki

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 40, issue 1, pages 53-59
Published in print January 1999 | ISSN: 0032-0781
Published online January 1999 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/oxfordjournals.pcp.a029474
Characterization of Cytosolic Cyclophilin from Guard Cells of Vicia faba L

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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 μM. 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 μM). This Ca2+-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.

Keywords: Calcineurin (EC 3.1.3.16); Cyclophilin (EC5.2.1.8); Cyclosporin A; Guard cell; Stomata; Vicia faba L

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Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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