Crystal structure of the human protein kinase CK2 regulatory subunit reveals its zinc finger-mediated dimerization

Abstract

Protein kinase CK2 is a tetramer composed of two α catalytic subunits and two β regulatory subunits. The structure of a C-terminal truncated form of the human β subunit has been determined by X-ray crystallography to 1.7 Å resolution. One dimer is observed in the asymmetric unit of the crystal. The most striking feature of the structure is the presence of a zinc finger mediating the dimerization. The monomer structure consists of two domains, one entirely α-helical and one including the zinc finger. The dimer has a crescent shape holding a highly acidic region at both ends. We propose that this acidic region is involved in the interactions with the polyamines and/or catalytic subunits. Interestingly, conserved amino acid residues among β subunit sequences are clustered along one linear ridge that wraps around the entire dimer. This feature suggests that protein partners may interact with the dimer through a stretch of residues in an extended conformation. Keywords: MAD method/protein kinase CK2/regulatory subunit/X-ray structure/zinc finger

Protein kinase CK2 regulates CDC25B phosphatase activity

“…For p53, the binding region includes the sequence between amino acids 71-149, in the case of DNA Topoisomerase IIa a central region (amino acids 51-110) was implicated and for Nopp 140, the first Nterminal 20 amino acids. This diversity of docking sites on CK2b, which differ from the catalytic centre of the enzyme, may represent a mechanism by means of which the enzyme increases its selectivity for protein substrates (Schulman et al, 1998;Chantalat et al, 1999). We also demonstrated that the region encompassing amino acids 123-200 of CDC25B contains the binding site for CK2b.…”

“…Procedures for the expression and purification of GST-CK2a-HA (Heriche et al, 1997) MBP-CK2b (Chantalat et al, 1999) and GST-CK2b fusion proteins have been previously described. Purified proteins were separated on a 12% polyacrylamide gel and transferred to PVDF membranes.…”

p53-dependent inhibition of mammalian cell survival by a genetically selected peptide aptamer that targets the regulatory subunit of protein kinase CK2

“…From a deletion study, we demonstrated that the N-terminal aa 1-55 represented the minimal region of CK2b for P1 peptide binding. This region, in the crystal structure of CK2b, is entirely a-helical (a1, a2, a3), extends at the surface of the molecule (Chantalat et al, 1999) and includes the putative destruction box and autophosphorylation sites (Litchfield, 2003). In agreement with the high-resolution structure of tetrameric CK2 (Niefind et al, 2001), the interaction of P1 with this region of CK2b neither dissociates the CK2 holoenzyme nor it prevents its formation.…”

“…The three-dimensional structure of the CK2b dimer has revealed the presence of solvent-exposed and -conserved residues that may represent binding surfaces for the multiple protein ligands previously identified as CK2b partners (Chantalat et al, 1999;Grein et al, 1999;Filhol et al, 2004). The identification of important protein kinases including A-Raf, c-Mos, Chk1 and Chk2 (Guerra et al, 1999b(Guerra et al, , 2003Bjorling-Poulsen et al, 2005) that interact with CK2b in the absence of catalytic CK2 subunits strongly suggests that CK2b has functions distinct from CK2a (Bibby and Litchfield, 2005).…”

Site-Directed Mutagenesis in the Research of Protein Kinases - The Case of Protein Kinase CK2

“…Results presented by several groups and obtained by the use of a variety of approaches, including X-ray crystallography, have determined that a dimer of the CK2 subunits forms the core of the CK2 tetramer (Chantalat et al, 1999;Sarno et al, 2000;Canton et al, 2001). …”