Consensus sequences, protein kinases

Protein kinases like glycogen-phosphorylase kinase act on specific amino-acid sequences, called consensus sequences. Protein-kinase-a acts on the serine/threonine residue in the sequence X-arg-arg/lys-X-ser/thr-asx. Cyclin-dependent-kinase-2 acts on the same residues in the sequence X-ser/thr-pro-X-lys/arg. Only the alcoholic amino acids serine, threonine and tyrosine can be phosphorylated. 

In addition to p53 and c-Jun, p27, ICSBP (interferon consensus sequence binding protein) and I/cBa were identified as substrates of the CSN-associated kinases (for a review see Ref [40]). Similar to p53, the phosphorylation of p27 results in... 

Identification of associated protein kinases Based on phosphopeptide analyses it became clear that associated kinases modify principally serine and threonine residues. Moreover, the analysis of putative phosphorylation-speciflc consensus sequences of p53, c-Jun, p27, ICSBP and I/cBa revealed that the protein kinase CK2 and a member of the protein kinase C family might be associated with the CSN. 

The invariant SQ motif in the C-terminus of H2AX is a consensus sequence for the 3 kinases belonging to the PIKK family, namely ATM, DNA-PK and ATR (Stiff et al, 2004). These kinases are involved in DNA repair. ATM [ataxia telangiectasia (A-T) mutated protein] is a crucial kinase for the signal transduction DSB pathway (Savitsky et al, 1995) and it is widely accepted that ATM is the major kinase involved in the in vivo phosphorylation of H2AX (Burma et al, 2001 Fernandez-Capetillo et al, 2002 Redon et al, 2002). The two other kinases were also associated with the generation y-H2AX, but they appeared not to be dominant (Redon et al, 2002 Stiff et al, 2004). 

Kennelly, P. J., and Krebs, E. G. (1991) Consensus sequences as substrate specificity determinants for protein kinases and protein phosphatases. J. Biol. Chem. 266, 15555-15558. 

The consensus sequence for phosphorylation of proteins by protein kinase A is RRXSX. The RII subrmit contains such a sequence in the autoinhibitory domain and is therefore subject to phosphorylation by the C subrmit in the holoenzyme, but without release of inhibition. Inhibition of the C subrmit by the R subrmit is based on binding of the autoinhibitory sequence of R at the substrate binding site and at parts of the active center of the C subrmit. 

In the absence of activating cofactors, the catalytic domain is subject to autoinhibition by the regulatory domain (Orr and Newton, 1994). A sequence motif is found in the regulatory domain which serves as a pseudosubstrate. It resembles the consensus sequence for phosphorylation sites of protein kinase C but does not have a Ser or Thr residue for phosphorylation. This sequence motif is found in aU protein kinase C family members. It is assumed that the active center is inhibited by occupation by the pseudosubstrate. 

The members of the protein kinase C family are central signal proteins and as such, are involved in the regulation of a multitude of cellular processes. A problem in the identification of substrates of protein kinase C is its low substrate specificity which often cannot be differentiated from that of protein kinase A, particularly in in vitro experiments. The consensus sequence of the phosphorylation sites in substrate proteins are similar to those of protein kinase A, in that basic amino acids are required in the neighborhood of the Ser/Thr residue to be phosphorylated. The following consensus sequences may be formulated for phosphorylation by protein kinase C ( = phosphorylation site) S /T XK/R K/RXXS /T K/RXXS /T XK/R K/RXS /T K/RXS /T XK/R (Pearson and Kemp, 1991). 

Pearson, R.B. and Kemp, B.E. Protein kinase phosphorylation site sequences and consensus specificity motifs tabulations (1991) Methods in Enzymol. 200, 62-81... 

Due to the problems in identification of cellular substrates of protein kinases, as described in Chapter 7, it has been a difficult and lengthy process to determine the functionally relevant substrates. Pig. 13.11 gives an overview of the ceU-cycle-specific activation of CDKs and some important substrates. Comparatively sparse information is available on the Gj and S phase substrates of the CDKs. In contrast, many proteins have been described that undergo specific phosphorylation in G2/M phase. The sequence (K/R)-S/T-P-X-K (X any amino acid) has been identified as a consensus sequence for phosphorylation by CDKs. 

ARK 1, substrate specificity, the overall topological structure of the activated receptor plays a key role in regulating signal-dependent receptor phosphorylation [14] <4> -ARK 1 substrate recognition mechanism, consensus sequence required for substrates, 3-dimensional model structure of the catalytic domain, potential phosphorylation sites of human 2-adrenergic receptor [20] <6,8> )3-ARK 1 is more active than /l-ARK 2 [21] <3> substrates wild-type and mutants of /I2-AR, synergistic action of /1-ARK and cAMP-dependent protein kinase depends on the pal-mitoylation state of the receptor, putative phosphorylation sites of 2-AR... 

The Ser, Thr, or T)yr residues that are phosphorylated in regulated proteins occur within common structural motifs, called consensus sequences, that are recognized by specific protein kinases (Table 6-10). Some kinases are basophilic, preferring to phosphorylate a residue having basic neighbors others have different substrate preferences, such as for a residue near a Pro residue. 

Protein kinase Consensus sequence and phosphorylated residue ... 

Sources Pinna, L.A. Ruzzene, M.H. (1996) How do protein kinases recognize their substrates Biochim. Biophys. Acta 1314, 191-225 Kemp, B.E. Pearson, R.B. (1990) Protein kinase recognition sequence motifs. Trends Biochem. Sc/. 15, 342-346 Kennelly, RJ, Krebs, E.G. (1991) Consensus sequences as substrate specificity determinants for protein kinases and protein phosphatases, J. Biol. Chem. 266, 15,555-15,558. 

The multivalency of signaling proteins allows for the assembly of many different combinations of signaling modules, each combination presumably suited to particular signals, cell types, and metabolic circumstances. The large variety of protein kinases and of phosphoprotein-binding domains, each with its own specificity (the consensus sequence required in its substrate), provides for many permutations and combinations and many different signaling circuits of extraordinary complexity. And given the variety of specific phosphatases that reverse... 

Pinna, L.A. Ruzzene, M. (1996) How do protein kinases recognize their substrates Biochvm. Biophys. Acta 1314, 191-225. Advanced review of the factors, including consensus sequences, that give protein kinases their specificity. 

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