The Saccharomyces cerevisiae Crs5 Metallothionein metal‐binding abilities and its role in the response to zinc overload

Abstract

Crs5 is a Saccharomyces cerevisiae Metallothionein (MT), non-homologous to the paradigmatic Cu-thionein Cup1. Although considered a secondary copper-resistance agent, we show here that it determines survival under zinc overload in a CUP1-null background. Its overexpression prevents the deleterious effects exhibited by CUP1-CRS5-null cells when exposed to combined Zn/Cu, as it does the mouse MT1 Zn-thionein, but not Cup1. The detailed characterization of Crs5 in vivo and in vitro Zn(II)-, Cd(II)- and Cu(I)-binding abilities fully supports its resemblance to mammalian MTs. Hence, Crs5 exhibits a good divalent metal-binding ability, yielding homometallic, highly chiral and stable Zn and Cd complexes when expressed in media enriched with these metal ions. In Cu-supplemented cultures, heterometallic Zn,Cu complexes are recovered, unless aeration is kept to a minimum. These features define a Crs5 dual metal-binding behaviour that is significantly closer to Zn-thioneins than to Cu-thioneins. Protein sequence similarities fully support these findings. Overall, a Crs5 function in global metal cell homeostasis, based on its Zn-binding features, is glimpsed. The comparative evaluation of Crs5 in the framework of MT functional differentiation and evolution allows its consideration as a representative of the primeval eukaryotic forms that progressively evolved to give rise to the Zn-thionein lineage.

Disruption of iron homeostasis in Saccharomyces cerevisiae by high zinc levels: a genome‐wide study

“…This is in contrast with the situation in S. pombe, which encodes the Zym1 Zn-thionein (Borrelly et al, 2002). In a recent characterization of the metal binding properties of Crs5, an unexpected toxic effect of the combination of zinc and copper was reported, which puts forward a connection between the zinc-and copper-handling pathways in this organism (Pagani et al, 2007).…”

“…MT can be classified, on the basis of their in vivo metal binding preferences and sequence features, as Zn-thioneins and Cu-thioneins (Valls et al, 2001). S. cerevisiae encodes the paradigmatic Cup1 Cu-thionein (Winge et al, 1998) and the dual Zn-Cu-thionein Crs5 (Pagani et al, 2007), but no specific zinc immobilizing protein is present in this organism. This is in contrast with the situation in S. pombe, which encodes the Zym1 Zn-thionein (Borrelly et al, 2002).…”

Different Patterns of Regulation for the Copper and Cadmium Metallothioneins of the Ectomycorrhizal Fungus Hebeloma cylindrosporum

“…Pagani et al (41), however, reported the involvement of the Crs5 Cu-metallothionein of S. cerevisiae in Zn detoxification. Tucker et al (47) described an MT-like protein in Magnaporthe grisea which showed a very high affinity to Zn.…”

“…The first one is encoded by the CUP1 locus and is induced by Cu and Ag but not by other heavy metals (8,40). The second one, Crs5, is regulated by Cu, Zn, and oxidative stress (14,41). An MT has been identified for Agaricus bisporus (37), Gigaspora margarita (29), Neurospora crassa (38), Pyrenopeziza brassicae (44), Podospora anserina (2), and P. involutus (6).…”

Chemically and Biologically Harmless versus Harmful Ferritin/Copper–Metallothionein Couples

“…preparations that result from the recombinant synthesis of MT2 and MT3 in Cusupplemented E. coli cultures grown under regular aeration, [20] which is the closest approximation to mammalian cell conditions. They yielded a mixture of Zn 1 Cu 10 -and Zn 2 Cu 10 -as major species for MT2 [17] and a mixture of Zn 4 Cu 6-and Cu 10 -complexes for MT3 [18] , which from now on and for the sake of simplicity we shall refer to as the Cu-MT2 and Cu-MT3 complexes.…”