Drosophila proteins interacting with metallothioneins: a metal-dependent recognition

Metallothioneins (MTs) are ubiquitous, low-molecular weight, cysteine-rich proteins. Despite a well-established protective role in metal excess detoxification, there is little data about their putative physiological functions, commonly assumed to be metal homeostasis and redox equilibrium. Protein-protein interactions should have provided useful information to unveil unsuspected functions, but reports on MT interactions are scarce. This is probably due to the MT metal-dependent 3D structure, a fact that has been seldom taken into account when performing proteomic interaction assays. In the present work, we have detected that the two major D. melanogaster isoforms (MtnA and MtnB) interact with the peroxiredoxin (Prx) encoded by the gene Jafrac1, both in a clear metal-dependent pattern. The MT-Prx interaction is further confirmed in Saccharomyces cerevisiae by assaying both yeast MTs (Crs5p and Cup1p) versus Tsa1p and Tsa2p, the Jafrac1 homologous Prxs in this organism. Thus, a new methodological approach to detect MT-interacting proteins in different proteomes is established on the basis of assaying MTs in the form of different metal complexes. Furthermore, new perspectives to investigate the often hypothesized contribution of MTs to the redox physiological networks are open.