Metallothionein zinc related

Pseudomonas putida growing on 3 mM cadmium synthesizes three cysteine-rich proteins of molecular weight 4000 to 7000, containing four to seven cadmium, zinc and copper atoms per molecule. The use of I13Cd NMR on the major cadmium protein shows it to be related to cadmium metallothionein, but with some significant differences.I223b... 

The second step in zinc absorption involves the intracellular interaction of zinc with various compounds which may enhance or impede absorptive processes. In 1969, Starcher noted that radioactive copper, given orally, associated with a low molecular weight protein (25). Subsequently, this mucosal protein was isolated and characterized by Richards and Cousins, who classified it as a metallothionein (26), and who further showed that it was induced in response to zinc administration (5). The appearance of this metallothionein, with properties similar to those described for both rat (27) and human (28) liver metallothionein, appears to be related to changes in both dietary zinc status and plasma zinc levels (5). The synthesis of mucosal metallothionein has been shown to be under transcriptional control (29,30). Menard al. reported that dietary zinc administration resulted in enhancement of metallothionein mRNA transcription and its subsequent translation, to yield nascent metallothionein polypeptides(31). The intestinal metallothionein appearance was correlated to both an increase in mucosal zinc content primarily associated with the protein and with a decrease in serum zinc levels. In addition. Smith e al., using the isolated, vascularly perfused intestinal system, reported an inverse relationship between the synthesis of metallothionein and zinc transfer to the portal system, confirming earlier studies (32). 

Sanders et al. (1983) have also shown that the effects of Cu(II) on the growth of crab larvae and on their metallothionein with copper chelate buffer systems must be interpreted on the basis of free Cu ion activity. The data obtained reveal predictable relations between [Cu ] in seawater and processes at the cellular and organismic levels. Similarly, the uptake of metal ions by plants (e.g., of aluminum) is usually related to free metal-ion activity. Others have shown that the chelation of a variety of metals reduces the toxicity of metals to organisms for example, a reduction in the uptake of mercury by fish in the presence of EDTA and cysteine a reduction in copper and/or zinc toxicity to... 

A striking feature of the cellular effects of bismuth compounds in animals (and one shared only by lead) is the production of intranuclear inclusion bodies of up to 5 ixm in diameter (87), for example, in the tubular epithelial cells of the kidney. Electron probe microanalysis shows that these contain both Bi and S, and so could be a complex with a Cys-rich protein such as metallothionein. Bismuth is known to be a potent inducer of renal metallothionein synthesis, and pretreatment of animals with bismuth salts can prevent some of the toxic side effects induced by cisplatin (88). The role of metallothionein in the pharmacology of bismuth remains to be established, but the strong involvement of zinc, also an inducer of metallothionein synthesis, in the metabolism of skin cells, for example, may be related. Like several other elements of Group V, the development of the biological chemistiy of Bi is hampered by the lack of good physical properties, in particular of a well-behaved NMR isotope. 

In mammalian cells, some proteins combine with specific metals which are called metal proteins. For instance, transferrin is an iron carrier, ferritin can store iron [9], metallothionein (MT) can hold divalent metals such as zinc, copper, cadmium and so on [10, 11]. In chromosomes, there are some regions where metal proteins combine and regulate gene expressions. Zinc-finger motif proteins are famous for regulating transcriptimi and translation [12]. These metal-related... 

It is also known that the toxic effects of heavy metals may be reduced in many organisms by binding to specific ligands. Metallothionein plays a crucial role among these specific ligands. In relation to trace elements, MT might serve as an indicator of an environmental pollution and exposure to this pollution. Increased level of MT-I and -II in tissue(s) indicates an exposure to trace elements, respectively heavy metals. MT-III is non-inducible and probably plays an important role in the metabolism of zinc and elements that are involved in neurotoxicity [128]. 

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