Phosphotyrosine as a specificity determinant for casein kinase-2, a growth related Ser/Thr-specific protein kinase.
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.
Meggio
F
F
Dipartimento di Chimica Biologica dell'Università di Padova, Italy.
Perich
J W
JW
Reynolds
E C
EC
Pinna
L A
LA
D000595:Amino Acid Sequence; D000818:Animals; D047388:Casein Kinases; D002455:Cell Division; D003600:Cytosol / Q000201:enzymology; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D010769:Phosphothreonine / Q000378:metabolism; D019000:Phosphotyrosine; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D013379:Substrate Specificity; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000502:physiology
D009842:Oligopeptides; D010769:Phosphothreonine; D010768:Phosphoserine; D019000:Phosphotyrosine; D014443:Tyrosine; D011494:Protein Kinases; D047388:Casein Kinases