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A synthetic β‐casein phosphopeptide and analogues as model substrates for casein kinase‐1, a ubiquitous, phosphate directed protein kinase
Author(s) -
Meggio Flavio,
Perich John W.,
Reynolds Eric C.,
Pinna Lorenzo A.
Publication year - 1991
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(91)80614-9
Subject(s) - phosphopeptide , casein , casein kinase 2 , phosphorylation , peptide , casein kinase 2, alpha 1 , chemistry , kinase , biochemistry , protein kinase a , enzyme , casein kinase 1 , substrate (aquarium) , stereochemistry , biology , cyclin dependent kinase 2 , ecology
The phosphopeptide Ser ( P )‐Ser( P )‐Ser‐( P )‐Glu‐Glu‐Ser 11 ‐Ilc‐Thr, reproducing the 17‐24 segment of β‐casein Λ 1 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 SIT 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 SIT ( 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.