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In vitro kinase assays
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We carried out in vitro kinase assays (except for Cdc28) in the presence of 0.2 μCi/μL [γ-32P]ATP at low ATP concentration (10 nM) so that IC50 values represent a rough measure of the inhibition constant (Ki). Measurement of inhibitor IC50 values were done as Liu, Y. et al. described. Purified Cdc28-His6 (1 nM) and MBP-Clb2 (3 nM) were incubated for 10 min at 23°C in a 25 μL reaction mixture containing 5 μg histone H1, 1 μCi of [γ-32P]ATP (1 μCi per 10 μM and 1μCi per 1 mM), and varying concentrations of 1-NM-PP1 in kinase buffer (25mM HEPES-NaOH pH 7.4, 10mM NaCl, 10mM MgCl2 and 1mM dithiothreitol). Reaction products were analysed by 15% SDS-PAGE followed by autoradiography. For the determination of Cdc28 kinetic constants, varying concentrations of [γ-32P] ATP (1 μCi per 100 μM) were incubated and analysed as above.
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References:
1. Bishop, A. C., Ubersax, J. A., Petsch, D. T., Matheos, D. P., Gray, N. S., Blethrow, J., Shimizu, E., Tsien, J. Z., Schultz, P. G., Rose, M. D., Wood, J. L., Morgan, D. O. and Shokat, K. M. (2000) A chemical switch for inhibitor-sensitive alleles of any protein kinase. Nature. 407, 395-401
2. Tamguney, T., Zhang, C., Fiedler, D., Shokat, K. and Stokoe, D. (2008) Analysis of 3-phosphoinositide-dependent kinase-1 signaling and function in ES cells. Exp Cell Res. 314, 2299-2312
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