Role of phosphorylated aminoacyl residues in generating atypical consensus sequences which are recognized by casein kinase-2 but not by casein kinase-1.
Casein kinase-2 (CK-2) is a ubiquitous Ser/Thr specific protein kinase that recognizes phosphorylatable residues located upstream of acidic determinants, its consensus sequence being Ser(Thr)-Xaa-Xaa-Acidic. Here we show that the phosphotetrapeptide AcSer(P)-Ser(P)-Ser-Ser(P), which is devoid of the canonical consensus sequence, is nevertheless phosphorylated by CK-2 with rates comparable to that of typical peptide substrates Ser-Glu-Glu-Glu-Glu-Glu and Arg-Arg-Arg-Glu-Glu-Glu-Thr-Glu-Glu-Glu routinely employed for assaying CK-2 activity. The phosphopeptide AcSer(P)-Ser-Ser(P) [but not Ac-Ser-Ser(P)-Ser(P) or AcSer(P)-Ser(P)-Ser] is also phosphorylated albeit less efficiently than AcSer(P)-Ser(P)-Ser-Ser(P). Further N-terminal elongation with additional phosphoseryl residues to give the peptides AcSer(P)-Ser(P)-Ser(P)-Ser-Ser(P) and AcSer(P)-Ser(P)-Ser(P)-Ser(P)-Ser-Ser(P) does not improve but rather slightly decreases the phosphorylation efficiency by CK-2. These two peptides are conversely excellent substrates for CK-1, which does not appreciably phosphorylate either AcSer(P)-Ser-Ser(P) or AcSer-(P)-Ser(P)-Ser-Ser(P). Either individual or multiple replacement of the phosphorylated residues with glutamic acid in the peptide AcSer(P)-Ser(P)-Ser-Ser(P) drastically reduces the phosphorylation efficiency by CK-2, the phosphoseryl residue at position -2 playing an especially crucial role which cannot be surrogated by glutamyl residues.(ABSTRACT TRUNCATED AT 250 WORDS)
Perich
J W
JW
Biochemistry and Molecular Biology Unit, School of Dental Science, University of Melbourne, Victoria, Australia.
Meggio
F
F
Reynolds
E C
EC
Marin
O
O
Pinna
L A
LA
D000595:Amino Acid Sequence; D047388:Casein Kinases; D007700:Kinetics; D008969:Molecular Sequence Data; D010748:Phosphopeptides / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
D010748:Phosphopeptides; D011494:Protein Kinases; D047388:Casein Kinases