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Phosphotyrosine as a specificity determinant for casein kinase‐2, a growth related Ser/Thr‐specific protein kinase

1991; Wiley; Volume: 279; Issue: 2 Linguagem: Inglês

10.1016/0014-5793(91)80174-2

1873-3468

Flavio Meggio, John W. Perich, Eric C. Reynolds, Lorenzo A. Pinna,

Biotin and Related Studies

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.