The C-terminal domain (residues 518-803) of the 94 kDa glucose regulated protein (grp94) was expressed in Escherichia coli as a fusion protein with a His6-N-terminal tag (grp94-CT). This truncated form of grp94 formed dimers and oligomers that could be dissociated into monomers by treatment with dithiothreitol. Grp94-CT conferred protection against aggregation on the catalytic subunit of protein kinase CK2 (CK2alpha), although it did not protect against thermal inactivation. This anti-aggregation effect of grp94-CT was concentration dependent, with full protection achieved at grp94-CT/CK2alpha molar ratios of 4 : 1. The presence of dithiothreitol markedly reduced the anti-aggregation effects of grp94-CT on CK2alpha without altering the solubility of the chaperone. It is concluded that the chaperone activity of the C-terminal domain of human grp94 requires the maintenance of its quaternary structure (dimers and oligomers), which seems to be stabilised by disulphide bonds.
European Journal of Biochemistry, 2001, Vol 268, Issue 2, p. 429-36
Casein Kinase II; Catalytic Domain; Disulfides; Dithiothreitol; HSP70 Heat-Shock Proteins; Humans; Membrane Proteins; Molecular Chaperones; Peptide Fragments; Protein Denaturation; Protein Structure, Quaternary; Protein Subunits; Protein-Serine-Threonine Kinases; Recombinant Fusion Proteins