Cross talk between protein kinase CK2 and eukaryotic translation initiation factor eIF2β subunit

The β-subunit of eukaryotic translation initiation factor eIF2 is a substrate and a partner for protein kinase CK2. Surface plasmon resonance analysis shows that the truncated form corresponding to residues 138-333 of eIF2β (eIF2β-CT) interacts with CK2α as efficiently as full length eIF2β, whereas the form corresponding to residues 1-137, which contains the CK2 phosphorylation sites, (eIF2β-NT) does not bind. The use of different mutants and truncated forms of CK2α allowed us to map the basic segment K74-K83 at the beginning of helix αC and residues R191R195K198 in the p+1 loop as the main determinants for the binding to eIF2β-CT of either the isolated CK2α subunit or the CK2 holoenzyme. The presence of eIF2β-CT stimulated the activity of CK2α towards the RRRAADSDDDDD peptide substrate; effect that was not observed with the CK2α K74-77A whose ability to bind to eIF2β-CT is severely impaired. Gel filtration analysis confirmed the ability of CK2α to form complexes with eIFα-CT, and the contribution of the basic cluster in CK2α (K74-K77) in this association. © Springer Science + Business Media, Inc. 2005.