Phosphoprotein phosphatase activity of Novikoff hepatoma nucleoli. |
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| Authors: | M O Olson K Guetzow |
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| Institution: | Nuclear Protein Laboratory, Department of Pharmacology, Baylor College of Medicine, Houston, Texas 77030 USA |
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| Abstract: | Nucleoli from Novikoff hepatoma ascites cells contain phosphatase activity that acts upon 32P-labeled nucleolar protein substrates. The activity is optimal near pH 7.0 and is inhibited by increasing concentrations of NaCl. The divalent cations CaCl2, MnCl2 and CoCl2 at 6 mM inhibited phosphatase activity from 30–60%. ZnCl2 completely inhibited the activity above 2 mM while EDTA and MgCl2 had little effect. The activity was stimulated by dithiothreitol and inhibited by N-ethylmaleimide indicating a requirement for free sulfhydryl groups. |
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