Copper-release from yeast Cu(I)-thionein by hypothiocyanite (OSCN?)

Abstract

In the course of an oxidative burst oxygen free radicals and hypothiocyanite (OSCN-), a transiently abundant derivative of thiocyanate (SCN-), are formed in the presence of activated polymorphonuclear leukocytes (PMNs). At the same time Cu(I)-thionein is present and the question arose whether or not thiocyanate and its oxidized form may transiently release highly Fenton active copper to improve the efficacy of the above mentioned oxidative burst. Thus, the reaction of yeast Cu-thionein with OSCN- was examined. Indeed, a release of copper from the Cu(I)-thiolate clusters of the protein was observed ex vivo. Both the chiroptic and luminescence emission signals of Cu-thionein essentially levelled off in the presence of a 15-fold molar excess of OSCN- expressed per equivalent of thionein-copper. The effective copper-releasing activity of this reagent was confirmed by equilibrium dialysis. The demetallized protein could be reconstituted under reductive conditions. SCN- did not affect the copper-thiolate bonding. It rather acts as a potent metabolic source for the transient copper release from Cu-thionein in the presence of activated PMNs.

Metallothionein: the multipurpose protein

“…MT-associated Cu is also important in the stress response, and this influence may extend to the extracellular environment, as demonstrated in vitro by the release of CuMT from peripheral blood monocytes during the oxidative burst [206]. Whereas CuMT has been shown to scavenge singlet oxygen and hydroxyl radicles and inhibit oxidative liver damage in galactosamine/endotoxin-induced hepatitis [207], Cu has been shown to be released from yeast CuMT by NO, making highly reactive Fenton Cu available during the oxidative burst [208]. Furthermore, MT has been shown in vitro to impair Cu-dependent lipid [209] and luminol [210] oxidation.…”

Nitric oxide releases intracellular zinc from prokaryotic metallothionein in Escherichia coli

“…NO elicits zinc release from transcription factors possessing zinc ¢ngers [17,18] in di¡erent eukaryotic cell lines [19] and in eukaryotic metallothioneins by destroying zinc^sulfur clusters [14,20,21]. These observations have signi¢cant implications for gene expression patterns in response to NO and for the possible role of metallothioneins in NO signalling [14,19].…”

Yeast Metallothionein in Transgenic Tobacco Promotes Copper Uptake from Contaminated Soils

“…While each soil pH was between 6.7 and 7.1, other soil constituents may lend to differential copper availability. Each soil may have constituents that promote or repress plant nitric oxide production, a gas known to regulate copper-MT binding (30). To better understand the differences in phytoextraction of the red and gray soils, a more extensive characterization of these soils types is necessary.…”