14-3-3 proteins activate a plant calcium-dependent protein kinase (CDPK) |
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Authors: | Lorenzo Camoni Jeffrey F Harper Michael G Palmgren |
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Institution: | aInstitute of Molecular Biology, University of Copenhagen, Øster Farimagsgade 2A, DK-1353 Copenhagen K, Denmark;bDepartment of Cell Biology, The Scripps Research Institute, 10666 North Torrey Pines Road, La Jolla, CA 92037, USA |
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Abstract: | Plants and protozoa contain a unique family of calcium-dependent protein kinases (CDPKs) which are defined by the presence of a carboxyl-terminal calmodulin-like regulatory domain. We present biochemical evidence indicating that at least one member of this kinase family can be stimulated by 14-3-3 proteins. Isoform CPK-1 from the model plant Arabidopsis thaliana was expressed as a fusion protein in E. coli and purified. The calcium-dependent activity of this recombinant CPK-1 was shown to be stimulated almost twofold by three different 14-3-3 isoforms with 50% activation around 200 nM. 14-3-3 proteins bound to the purified CPK-1, as shown by binding assays in which either the 14-3-3 or CPK-1 were immobilized on a matrix. Both the 14-3-3 binding and activation of CPK-1 were specifically disrupted by a known 14-3-3 binding peptide LSQRQRSTpSTPNVHMV (IC50=30 μM). These results raise the question of whether 14-3-3 can modulate the activity of CDPK signal transduction pathways in plants. |
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Keywords: | 14-3-3 protein Calcium-dependent protein kinase Signal transduction |
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