DUK114, the Drosophila orthologue of bovine brain calpain activator protein, is a molecular chaperone.

TitleDUK114, the Drosophila orthologue of bovine brain calpain activator protein, is a molecular chaperone.
Publication TypeJournal Article
Year of Publication2004
AuthorsFarkas, A., G. Nardai, P. Csermely, P. Tompa, and P. Friedrich
JournalBiochem J
IssuePt 1
Date Published2004 Oct 1
KeywordsAmino Acid Sequence, Animals, Calpain, Cattle, Cell Line, Citrate (si)-Synthase, Cloning, Molecular, Drosophila melanogaster, Drosophila Proteins, Hot Temperature, Membrane Proteins, Molecular Chaperones, Molecular Sequence Data, Protein Conformation, Protein Denaturation, Protein Renaturation, Recombinant Fusion Proteins, Sequence Homology, Amino Acid

UK114, the goat liver tumour antigen, is a member of a widely distributed family of conserved low-molecular-mass proteins (YER057c/YjgF/UK114), the function of which is ill understood. To the various orthologues diverse functions have been ascribed, such as translation inhibition, regulation of purine repressor or calpain activation. Owing to a limited sequence similarity to Hsp90 (heat-shock protein 90), they have also been proposed to be molecular chaperones; however, this has never been tested. In the present paper, we report the cloning and characterization of the Drosophila orthologue, DUK114. In brief, DUK114 had no effect that would have qualified it as a calpain activator. In contrast, it proved to be a very potent molecular chaperone in in vitro assays. In a heat-aggregation test, it significantly decelerated the formation of citrate synthase aggregates. In a reverse assay, the recovery of the enzyme from urea- and heat-induced denatured states was accelerated almost 3-fold. On a molar basis, the chaperone activity of the 15-kDa DUK114 is comparable with that of Hsp90, the almost 6-times-larger archetypal molecular chaperone. In similar assays, DUK114 was ineffective with Drosophila calpain A or calpain B. To test for its chaperone activity in vivo, DUK114 was transfected into Schneider (S2) cells; after heat shock, the number of viable non-transfected cells started to increase after a lag time; in the presence of DUK114, cell proliferation started at once. Our work is the first experimental evidence that DUK114, and possibly other members of this family, are molecular chaperones.

Alternate JournalBiochem. J.
PubMed ID15250825
PubMed Central IDPMC1134055