The stability and function of human cochaperone Hsp40/DNAJA1 are affected by zinc removal and partially restored by copper.

The imbalance in metal homeostasis can be associated with several human diseases, and exposure to increasing concentrations of metals promotes cell stress and toxicity. Therefore, understanding the cytotoxic effect of metal imbalance is important to unravel the biochemical mechanism of homeostasis and the action of potential protective proteins against metal toxicity. Several studies, including gene deletion in yeast, provide evidence indicating the possible indirect involvement of cochaperones from the Hsp40/DNAJA family in metal homeostasis, possibly through modulating the activity of Hsp 70.This work first investigated the effect of zinc and copper on the conformation and function of the human Hsp40 cochaperone DNAJA1, a zinc-binding protein. DNAJA1 was capable to complement the phenotype of a yeast strain deleted of the ydj1 gene, which was more sensitive to the presence of zinc and copper than the wild-type strain. To gain further insight about the role of the DNAJA family in metal binding, the recombinant human DNAJA1 protein was studied. Zinc removal from DNAJA1 affected both its stability and ability to act as a chaperone, i.e., to protect other proteins from aggregation. The reintroduction of zinc restored the native properties of DNAJA1 and, surprisingly, the addition of copper partially restored the native properties.