The crystal structure of yeast copper thionein: The solution of a long-lasting enigma

Abstract

We report here the crystal structure of yeast copper thionein (Cu-MT), determined at 1.44-Å resolution. The Cu-MT structure shows the largest known oligonuclear Cu(I) thiolate cluster in biology, consisting of six trigonally and two digonally coordinated Cu(I) ions. This is at variance with the results from previous spectroscopic determinations, which were performed on MT samples containing seven rather than eight metal ions. The protein backbone has a random coil structure with the loops enfolding the copper cluster, which is located in a cleft where it is bound to 10 cysteine residues. The protein structure is somewhat different from that of Ag7-MT and similar, but not identical, to that of Cu7-MT. Besides the different structure of the metal cluster, the main differences lie in the cysteine topology and in the conformation of some portions of the backbone. The present structure suggests that Cu-MT, in addition to its role as a safe depository for copper ions in the cell, may play an active role in the delivery of copper to metal-free chaperones.copper metabolism ͉ metallothionein ͉ Saccharomyces cerevisiae ͉ x-ray structure

Visualizing Biological Copper Storage: The Importance of Thiolate‐Coordinated Tetranuclear Clusters

“…To prevent toxicity, eukaryotes store excess cytosolic copper using metallothioneins (MTs) 2, 3, 4, 5. The ability of bacteria to maintain appreciable amounts of intracellular copper has only recently been discovered 6, 7.…”

Mixed valence copper–sulfur clusters of highest nuclearity: a Cu8 wheel and a Cu16 nanoball

“…The CuA site reduces the MV CuZ to a fully reduced (µ4-S)Cu I 4 cluster that acts as the catalytic site for N2O reduction to N2. Also, Cu I mS thiol n clusters (m = 4, 6 and 8) are found in the copper metallothionein 7 proteins that function as storage, transport, metabolism and acquisition of Cu in biological systems.…”

Crystallization of soluble proteins in vapor diffusion for x-ray crystallography

“…This is one of the most powerful tools available 25,26 , and it might represent the key factor to achieve crystallization in the most difficult cases 24 . However, be aware that the mutated protein is by definition different from the 'wild-type' and the influence of the introduced mutation(s) on the protein chemical behavior should be evaluated thoroughly (see ANTICIPATED RESULT for an example).…”

“…Our suggestion is to characterize the protein as much as possible beforehand. For example, in our experience, in the more difficult cases, it is extremely useful to perform nuclear magnetic resonance (NMR) measurements to ascertain the presence of mobile (or even unfolded) parts or domains of the protein in order to plan mutagenesis experiments 24 (see ANTICIPATED RESULTS). Mutagenesis is a formidable tool to achieve protein crystallization 25,26 .…”