A synthetic β‐casein phosphopeptide and analogues as model substrates for casein kinase‐1, a ubiquitous, phosphate directed protein kinase

FEBS Letters

Pinna, Lorenzo A.¹  Reynolds, Eric C.²  Meggio, Flavio¹  Perich, John W.² 

[1] Dipartimento di Chimica Biologica, Universitá di Padova, Italy;Biochemistry and Molecular Biology Unit, School of Dental Science, The University of Melbourne, Australia

关键词: Phosphopeptide;    Protein kinase specificity;    Casein kinase-1;    β-Casein;    CK-1;    casein kinase-1;    CK-2;    casein kinase-2;    Ser(P);    phosphoserine where one-letter symbols for amino acids are used Sp denotes phosphoserine;   

DOI  :  10.1016/0014-5793(91)80614-9

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The phosphopeptide Ser (P)-Ser(P)-Ser-(P)-Glu-Glu-Ser¹¹-Ilc-Thr, reproducing the 17-24 segment of β-casein Λ¹ including the seryl residue (Ser-22) which is targeted by casein kinase-1 was synthesized and used as model substrate for this enzyme. Its phosphorylation efficiency is actually higher than that of intact β-casein (similar V_max and 14 μM vs 50 μM K_m ). Conversely the fully dephosphorylated peptide SSSEESIT is not affected by CK-1 to any detectable extent and its glutamyl derivative EEEEESIT displays a more than 50-fold higher K_m and a 5-fold lower V_max as compared to the parent phosphopeptide. The relevance of the individual phosphoseryl residues has been assessed by comparing the phosphorylation efficiencies of the phosphopeptides EESpEESIT, ESpEEESIT and SpEEEESIT; while the first is a substrate almost as good as the tris Ser (P)-peptide (K_m =62 μM), and the third one is almost as poor as EEEEESIT (K_m =1.55mM), ESpEEESIT displays a intermediate efficiency (K_m =277 μM). These data in conjunction with the finding that the phosphopentapeptide Ser(P)-Ser(P)-Ser-(P)-Ser-Ser(P), but neither Ser(P)-Ser(P)-Ser-Ser(P) nor Ser-Ser(P)-Ser(P)-Glu-Glu and Ser-Ala-Ala-Ser(P)-Ser(P), is readily phosphorylated by CK-1, support the concept that CK-1 is a phosphate directed protein kinase recognizing the Ser(P)-X-X-Ser-X and, less efficiently, the Ser(P)-X-X-X-Ser-X motifs.

【 授权许可】

Unknown