Catalytic properties of a human cytomegalovirus-induced protein kinase
Autor: | Octavian Bârzu, Maryse Tardy-Panit, Susan Michelson |
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Rok vydání: | 1985 |
Předmět: |
Glycerol
Cytomegalovirus Mitogen-activated protein kinase kinase Phosvitin Biology Biochemistry Catalysis MAP2K7 Substrate Specificity Cytosol Casein kinase 2 alpha 1 Humans Magnesium Phosphorylation Protein kinase A Protein Kinase Inhibitors Binding Sites Autophosphorylation Caseins Fibroblasts Hydrogen-Ion Concentration Cell Transformation Viral Molecular biology Enzyme Activation Enzyme Induction Casein kinase 1 Casein kinase 2 Protein Kinases Subcellular Fractions |
Zdroj: | European journal of biochemistry. 149(2) |
ISSN: | 0014-2956 |
Popis: | Human cytomegalovirus, a DNA virus whose genome contains a fragment of transforming DNA, induces a threonine-serine protein kinase having a molecular mass of 68 kDa (p68). p68 was extracted from cells 96–144 h after infection, and immunoprecipitated with a monoclonal antibody (F6b). Antibody-enzyme complexes were immobilized on heat/formaldehyde-inactivated Staphylococcus aureus. The best substrates for p68 were acidic proteins, phosvitin and casein. Glycogen synthase, phosphorylase a and histones were phosphorylated at rates not higher than 1–4% that obtained with phosvitin as substrate. ATP and GTP were equally good substrates of p68. p68 is able to autophosphorylate at the same residues (i.e. threonine and serine) as the protein substrates. Autophosphorylation does not seem to represent an intermediate in substrate phosphorylation. The protein kinase activity of p68 was not enhanced by cAMP, calcium ions, or polyamines like spermine or spermidine. Only at low Mg2+ concentration spermine enhanced by 68% the rate of casein phosphorylation. Heparin, a potent inhibitor of casein kinase II, inhibits p68 activity too, but ten-times higher concentrations were required for the same degree of inhibition. Quercetin, a bioflavonoid, acts as a strong inhibitor of p68 protein kinase activity. The inhibitory effect of quercetin was competitive towards the nucleotide substrate (Ki= 2.8 μM), and non-competitive towards the protein substrate (Ki= 15 μM). |
Databáze: | OpenAIRE |
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