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  • Title: Phosphotyrosine as a specificity determinant for casein kinase-2, a growth related Ser/Thr-specific protein kinase.
    Author: Meggio F, Perich JW, Reynolds EC, Pinna LA.
    Journal: FEBS Lett; 1991 Feb 25; 279(2):307-9. PubMed ID: 1705898.
    Abstract:
    The motif Ser-Ser-Ser-Glu-Glu is readily phosphorylated by casein kinase-2 (CK-2), a growth-related protein kinase whose consensus sequence is Ser(Thr)-Xaa-Xaa-Glu(Asp) [(1990) Biochim. Biophys. Acta 1054, 267-283]. Here we show that phosphotyrosine can replace carboxylic acids as specificity determinant for CK-2 phosphorylation, the phosphotyrosyl peptide Ser-Ser-Ser-TyrP-TyrP actually being a substrate more efficient than Ser-Ser-Ser-Glu-Glu itself both in terms of Km (0.69 vs 2.43 mM) and Vmax. Prior dephosphorylation of phosphotyrosine entirely prevents the subsequent phosphorylation of serine by CK-2. While Ser-Ser-Ser-TyrP-TyrP is a better substrate than Ser-Ser-Ser-SerP-SerP, which in turn is better than Ser-Ser-Ser-Glu-Glu, Ser-Ser-Ser-ThrP-ThrP is a less efficient substrate than Ser-Ser-Ser-Glu-Glu. Thus the order of efficiency of phosphoamino acids as specificity determinants for CK-2 appears to be TyrP greater than SerP much greater than ThrP.
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