title: Cadmium resistance conferred to yeast by a non-metallothionein-encoding gene of the earthworm Enchytraeus.
abstract: The earthworm Enchytraeus is able to survive in cadmium (Cd)-polluted environments. Upon Cd exposure, the worms express a gene encoding the putative non-metallothionein 25-kDa cysteine-rich protein (CRP), which contains eight repeats with highly conserved cysteines in Cys-X-Cys and Cys-Cys arrangements exhibiting 36-53% identities to the 6-7-kDa metallothioneins of different organisms. Here, we demonstrate that the CRP protein confers a highly Cd-resistant phenotype to a Cd-hypersensitive yeast strain. Cd resistance increases with increasing numbers of expressed CRP repeats, but even one 3-kDa CRP repeat still mediates Cd resistance. Site-directed mutagenesis reveals that each single cysteine within a given repeat is important for Cd resistance, though to a different extent. However, replacement of other conserved amino acids such as Pro(136) and Asp(196) at the CRP repeat junctions does not affect Cd resistance. Our data indicate (i) that the non-metallothionein CRP protein is able to detoxify Cd and (ii) that this is dependent on the availability of sulfhydryl groups of the conserved cysteines.
authors.affiliation: Division of Molecular Parasitology and Centre of Biological-Medical Research and the Institute of Morphology, Cell Biology, and Parasitology, Heinrich-Heine-University, Universitaetsstrasse 1, 40225 Duesseldorf, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Tschuschke
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Schmitt-Wrede
authors.forename: Hartmut
authors.initials: H
authors.lastname: Greven
authors.forename: Frank
authors.initials: F
authors.lastname: Wunderlich
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry; D015153:Blotting, Western; D002104:Cadmium / Q000378:metabolism* / Q000494:pharmacology*; D003545:Cysteine / Q000737:chemistry; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D008668:Metallothionein / Q000378:metabolism*; D051379:Mice; D018613:Microscopy, Confocal; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009835:Oligochaeta; D010641:Phenotype; D011392:Proline / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid
chemical_list: C098993:CRP protein, earthworm; D018076:DNA, Complementary; D011506:Proteins; D002104:Cadmium; D001224:Aspartic Acid; D008668:Metallothionein; D011392:Proline; D003545:Cysteine