title: The regulatory beta subunit of protein kinase CK2 contributes to the recognition of the substrate consensus sequence. A study with an eIF2 beta-derived peptide.
abstract: CK2 is a ubiquitous and pleiotropic Ser/Thr-specific protein kinase that phosphorylates more than 300 protein substrates at sites specified by an acidic consensus sequence in which positions n + 3 and n + 1 are particularly important. Recognition of substrates by CK2 is known to rely on basic residues located in the catalytic site of the alpha subunit which make electrostatic contacts with the negative charges in the substrate consensus sequence, thereby assuring optimal binding; the regulatory beta subunit is believed to play a protective and stabilizing role. We describe a biochemical and structural analysis of CK2-mediated phosphorylation of a 22-mer synthetic peptide corresponding to the N-terminal tail of the eukaryotic translation initiation factor eIF2beta. Results demonstrate that this peptide still displays phosphorylation features similar to full-length eIF2beta and the CK2 beta subunit also contributes to recognition of the protein substrate by establishing both polar and hydrophobic interactions with specificity determinants located downstream from the phosphoacceptor site. In particular, the N-terminal domain of the beta subunit appears to be of crucial importance for optimizing high-affinity phosphorylation of the eIF2beta peptide. This domain includes an acidic cluster whose electrostatic contacts with basic residues of the substrate attenuate intrasteric pseudosubstrate inhibition while strengthening substrate-kinase binding.
authors.affiliation: Department of Biological Chemistry and CNR Institute of Neurosciences, University of Padova, viale G. Colombo 3, 35131 Padova, Italy.
authors.forename: Giorgia
authors.initials: G
authors.lastname: Poletto
authors.forename: Jordi
authors.initials: J
authors.lastname: Vilardell
authors.forename: Oriano
authors.initials: O
authors.lastname: Marin
authors.forename: Mario A
authors.initials: MA
authors.lastname: Pagano
authors.forename: Giorgio
authors.initials: G
authors.lastname: Cozza
authors.forename: Stefania
authors.initials: S
authors.lastname: Sarno
authors.forename: Antoni
authors.initials: A
authors.lastname: Falqués
authors.forename: Emilio
authors.initials: E
authors.lastname: Itarte
authors.forename: Lorenzo A
authors.initials: LA
authors.lastname: Pinna
authors.forename: Flavio
authors.initials: F
authors.lastname: Meggio
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D047390:Casein Kinase II / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain / Q000235:genetics; D016384:Consensus Sequence; D020717:Eukaryotic Initiation Factor-2B / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D013379:Substrate Specificity
chemical_list: D020717:Eukaryotic Initiation Factor-2B; D010446:Peptide Fragments; D047390:Casein Kinase II