The carboxy-terminal domain of Grp94 binds to protein kinase CK2 alpha butnot to CK2 holoenzyme

Surface plasmon resonance. analysis shows that the carboxy-terminal domain of Grp94 (Grp94-CT, residues 518-803) physically interacts with the catalyt ic subunit of protein kinase CK2 (CK2 alpha) under non-stressed conditions. A K-D of 4X10(-7) was determined for this binding. Heparin. competed with Grp94-CT for binding to CK2 alpha. CK2 beta also inhibited the binding of G rp94-CT to CK2 alpha, and CK2 holoenzyme reconstituted in vitro was unable to bind Grp94-CT. The use of CK2 alpha mutants made it possible to map the Grp94-CT binding site to the four lysine stretch (residues 74-77) present i n helix C of CK2 alpha. Grp94-CT stimulated the activity of CK2 alpha wild- type but was ineffective on the CK2 alpha K74-77A mutant. (C) 2001 Federati on of European Biochemical Societies. Published by Elsevier Science B.V. Al l rights reserved.