Multiple forms of cytosol and membrane-bound protein kinase activity in human erythrocytes

1. Cyclic AMP-stimulated protein kinase activity phosphorylating intrinsic substrates in preparations of synaptic-membrane fragments from ox cerebral cortex was examined in relation to (a) the content of membrane-bound Ca2+in the preparations and (b) added Ca2+in the assay medium. 2. Centrifugal washing of synaptic-membrane fragments with buffered ethane dioxybis(ethylamine)tetra-acetate solutions decreased bound Ca2+from 2.8±0.4 (s.d.) to 0.9±0.3nmol/mg of protein. In washed preparations basal protein kinase activity was increased by about 40% and the cyclic AMP-stimulated activity by about 15%. Addition of Ca2+in the concentration range 5–50μm to the assay medium progressively inhibited the kinase activity of the washed preparations; in this range of Ca2+concentration the basal activity was inhibited more than the stimulated activity. 3. In unwashed preparations concentrations of Ca2+above 100μm inhibited the cyclic AMP-stimulated activity more than the basal activity. 4. The inhibitory effect of several concentrations of Ca2+was examined in relation to cyclic AMP concentration; no evidence for competition between Ca2+and cyclic AMP for a site on the enzyme was observed.

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Membrane-bound protein kinase activity in Jerusalem artichoke rhizome tissues

Plant Science Letters ◽

10.1016/0304-4211(79)90143-3 ◽

1979 ◽

Vol 15 (4) ◽

pp. 373-385 ◽

Cited By ~ 3

Author(s):

M. Giannattasio ◽

G.F. Tucci ◽

G. Carratù ◽

Ponzi

Keyword(s):

Protein Kinase ◽

Kinase Activity ◽

Jerusalem Artichoke ◽

Protein Kinase Activity ◽

Membrane Bound

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Effect of Thrombin on Phosphorylation of Platelet Membrane Proteins

Thrombosis and Haemostasis ◽

10.1055/s-0038-1647962 ◽

1976 ◽

Vol 35 (03) ◽

pp. 635-642 ◽

Cited By ~ 4

Author(s):

M Steiner

Keyword(s):

Protein Kinase ◽

Kinase Activity ◽

Qualitative Change ◽

Protein Kinase Activity ◽

Protein Substrates ◽

Phosphoprotein Phosphatase ◽

Progressive Loss ◽

Platelet Membranes ◽

Endogenous Protein ◽

Considerable Loss

SummaryThe effect of thrombin on the phosphorylating activity of platelet membranes was compared to that of trypsin. Preincubation of non-32P phosphorylated platelet membranes with or without either of these two enzymes resulted in a considerable loss of membrane protein kinase activity which was most severe when trypsin was used. Protein kinase activity and endogenous protein acceptors decreased in parallel. 32P-phosphorylated membranes showed a slow but progressive loss of label which was accelerated by trypsin. Thrombin under these conditions prevented the loss of 32P-phosphate. These results are interpreted to indicate a thrombin-induced destruction of a phosphoprotein phosphatase. The protein kinase activity of phosphorylated platelet membranes using endogenous or exogenous protein substrates showed a significant reduction compared to non-phosphorylated membranes suggesting a deactivation of protein kinase by phosphorylation of platelet membranes. Neither thrombin nor trypsin caused a qualitative change in the membrane polypeptides accepting 32P-phosphate but resulted in quantitative alterations of their ability to become phosphorylated.

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