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Keywords:

Alkaline Phosphatase, Amino Acid Sequence, Animals, Arachidonic Acid, Carrier Proteins, Casein Kinase II, Chromatography, DEAE-Cellulose, Kinetics, Magnesium, Manganese, Microfilament Proteins, Molecular Sequence Data, Phosphoprotein Phosphatase, Physarum polycephalum, Protein-Serine-Threonine Kinases, Research Support, Non-U.S. Gov't, Serine, Substrate Specificity, Science & Technology, Life Sciences & Biomedicine, Biochemistry & Molecular Biology, Biophysics, actin-binding protein, PP2C, plasmodial fragmin, Physarum, RABBIT SKELETAL-MUSCLE, SERINE THREONINE PHOSPHATASES, ACTIN-BINDING PROTEIN, CRYSTAL-STRUCTURE, PURIFICATION, 2C, POLYCEPHALUM, COMPLEX, GELSOLIN, ENZYME, Phosphoprotein Phosphatases, Protein Serine-Threonine Kinases, 0304 Medicinal and Biomolecular Chemistry, 0601 Biochemistry and Cell Biology, 1101 Medical Biochemistry and Metabolomics, 3101 Biochemistry and cell biology, 3404 Medicinal and biomolecular chemistry

Abstract:

Plasmodial fragmin, a Physarum polycephalum F-actin severing and capping protein, is phosphorylated by casein kinase II at Ser(266) (De Corte, V., Gettemans, J., De Ville, Y., Waelkens, E., and Vandekerckchove, J. (1996), Biochemistry 35, 5472-5480). In this study, we report the purification and characterization of the corresponding fragmin phosphatases. One of the enzymes was purified to near homogeneity from a cytosolic extract; it dephosphorylates CKII-phosphorylated fragmin, a peptide encompassing the CKII phosphorylation site of fragmin as well as histone 2A, CKII-phosphorylated casein and the CKII model-peptide substrate: R(3)E(3)S(P)E(3). Its activity was highly stimulated by Mn(2+) and Mg(2+), and based on its lack of sensitivity toward phosphatase effectors we could exclude similarities with PP1, PP2A and PP2B phosphatases. All biochemical properties of the phosphatase point to a PP2C-like enzyme. A second phosphatase dephosphorylating fragmin was identified as a Physarum alkaline phosphatase.