caa a22 4500 397557795 CHVBK 20180308164807.0 cr unu---uuuuu 161202e199605 xx s 000 0 eng 10.1093/oxfordjournals.jbchem.a021315 doi (NATIONALLICENCE)oxford-10.1093/oxfordjournals.jbchem.a021315 Studies on the Phosphorylation of a Mr 25,000 Protein, a Putative Protein Phosphatase 2A Modulator, by Casein Kinase I, and Analysis of Multiple Endogenous Phosphates [Elektronische Daten] [Ying Liu, Hiromi Kohara, Eikichi Hashimoto] A Mr 25,000 protein, which was isolated from the cytosolic fraction of Xenopus laevis oocytes, is a newly identified substrate for casein kinase II and protein kinase C [Hashimoto et al. (1995) J. Biochem. 118, 453-460], and was recently shown to have the ability to modulate protein phosphatase 2A activity [Hashimoto et al. (1996) J. Biochem. 119, 626-632]. Acid phosphatase treatment of the protein shifted its electrophoretic mobility from 25 to 20 kDa on SDS-PAGE. The content of alkali-labile phosphate bound covalently to the protein was 53 mol per mol of Mr 25,000 protein. Amino acid composition analysis revealed that there are 50 serine residues and 6 threonine residues per mol of this protein. Therefore, this Mr 25,000 protein seems to be highly phosphorylatedin vivo. The Mr 25,000 protein, once partially dephosphorylated by acid phosphatase, served as an efficient substrate for casein kinase I and casein kinase II. When entirely dephosphorylated, the Mr 25,000 protein was used as a substrate, the rate of phosphorylation with both casein kinases being decreased. This behavior of casein kinases toward the Mr 25,000 protein reflects the possible mechanism of multisite phosphorylation in which the introduction of a phosphate group facilitates sequential phosphorylation. © by the Journal of Biochemistry Regular Papers nationallicence casein kinase I nationallicence endogenous phosphate nationallicence multisite phosphorylation nationallicence protein phosphorylation nationallicence Xenopus laevis oocyte nationallicence Liu Ying Department of Pathological Biochemistry, School of Life Sciences, Faculty of Medicine, Tottori University, Nishimachi 86, Yonago, Tottori 683 aut Kohara Hiromi Department of Pathological Biochemistry, School of Life Sciences, Faculty of Medicine, Tottori University, Nishimachi 86, Yonago, Tottori 683 aut Hashimoto Eikichi Department of Pathological Biochemistry, School of Life Sciences, Faculty of Medicine, Tottori University, Nishimachi 86, Yonago, Tottori 683 aut The Journal of Biochemistry Oxford University Press 119/5(1996-05), 1004-1013 0021-924X 119:5<1004 1996 119 jbchem https://doi.org/10.1093/oxfordjournals.jbchem.a021315 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1093/oxfordjournals.jbchem.a021315 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Liu Ying Department of Pathological Biochemistry, School of Life Sciences, Faculty of Medicine, Tottori University, Nishimachi 86, Yonago, Tottori 683 aut NATIONALLICENCE 700 1- Kohara Hiromi Department of Pathological Biochemistry, School of Life Sciences, Faculty of Medicine, Tottori University, Nishimachi 86, Yonago, Tottori 683 aut NATIONALLICENCE 700 1- Hashimoto Eikichi Department of Pathological Biochemistry, School of Life Sciences, Faculty of Medicine, Tottori University, Nishimachi 86, Yonago, Tottori 683 aut NATIONALLICENCE 773 0- The Journal of Biochemistry Oxford University Press 119/5(1996-05), 1004-1013 0021-924X 119:5<1004 1996 119 jbchem Metadata rights reserved CC BY-NC-4.0 http://creativecommons.org/licenses/by-nc/4.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-oxford