Synthesis of Metallothionein-like Peptides Cadystin A and B Occurring in a Fission Yeast, and Their Isomers

Kondo, Naoto; Isobe, Mitsuaki; Imai, Kunio; Goto, Toshio

doi:10.1080/00021369.1985.10866670

Cited by 13 publications

(16 citation statements)

References 5 publications

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“…In higher plants the metal-binding polypeptide phytochelatin [10], also known as cadystin [22], poly-7(EC)nG [19] and Cde+-binding polypeptide [35], has been suggested to act as a functional analogue of metallothionein [ 11 ]. Synthesis of phytochelatin is induced by Cd 2÷ and several other metal ions including Zn 2÷ [9].…”

Section: Introductionmentioning

confidence: 99%

Expression of the type 2 metallothionein-like gene MT2 from Arabidopsis thaliana in Zn2+-metallothionein-deficient Synechococcus PCC 7942: putative role for MT2 in Zn2+ metabolism

1996

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Zn2+ proteins pervade metabolism and are essential for gene expression. However, no proteins have been ascribed the central roles of Zn2+ donation to, or removal from, metalloproteins, or Zn2+ storage in vegetative plant tissue. In animals, such functions have been proposed for metallothioneins. Plants contain multiple metallothionein-like genes but their predicted products, which differ significantly from animal metallothioneins, remain to be isolated from vegetative tissue and their roles are uncertain. The type 2 metallothionein-like gene from Arabidopsis, MT2, was expressed under the control of Zn2+-responsive elements derived from the cyanobacterial metallothionein divergon, smt. Zn2+-dependent expression of MT2 transcripts in Synechococcus PCC 7942 was confirmed by northern analysis. The Arabidopsis MT2 gene partly complemented Zn2+ hypersensitivity in mutants of Synechococcus PCC 7942 which are functionally deficient in an endogenous Zn2+-metallothionein gene, smtA. MT2 was also expressed as a recombinant fusion protein in Escherichia coli, purified and shown to bind Zn2+ in vitro. The mean pH of half displacement of Zn2+ from MT2 was estimated to be 5.05. This suggests that MT2 has a greater affinity for Zn2+ than phytochelatins. The results presented here reveal that MT2 is capable of binding Zn2+ in vitro, conferring tolerance to elevated [Zn2+] in vivo within cyanobacteria and is likely to compete with other polypeptides for cellular Zn2+ in planta.

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Section: Introductionmentioning

confidence: 99%

Expression of the type 2 metallothionein-like gene MT2 from Arabidopsis thaliana in Zn2+-metallothionein-deficient Synechococcus PCC 7942: putative role for MT2 in Zn2+ metabolism

1996

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“…These polypeptides are synthesized from glutathione and/or 7-glutamylcysteine precursors and their synthesis increases in response to elevated levels of certain toxic trace metals [13,14]. There is evidence that a function of (7EC),G, also termed class III MT [ 15], phytochelatin [ 16] or cadystin [17,18], is to detoxify supra-optimal concentrations of certain metal ions (notably Cd and Cu) and it has been proposed that they may be functional analogues of MTs (class I and II) in plants. Recent evidence suggests, however, that higher plants also possess MT genes.…”

Section: Introductionmentioning

confidence: 99%

Expression of the pea metallothionein-like gene PsMT A in Escherichia coli and Arabidopsis thaliana and analysis of trace metal ion accumulation: Implications for PsMT A function

et al. 1992

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The PsMTA gene from pea (Pisum sativum) shares similarity with metallothionein (MT) genes and related sequences have also been isolated from a number of other higher-plant species. The proteins encoded by these genes have not yet been purified from plants and their functions remain unclear although, by analogy to MT, roles in the metabolism and detoxification of metal ions have been proposed. By contrast, correlation between transcript abundance and Fe availability has led to an alternative proposal that these genes are involved in mechanisms of Fe efficiency. Phenotypic effects of constitutive PsMTA expression were examined in Escherichia coli and Arabidopsis thaliana. Copper accumulation by E. coli cells expressing recombinant PsMTA protein was approximately 8-fold greater than in control cells. No significant effects on the accumulation of Zn or Cd were detected. In segregating A. thaliana progeny, derived from a transgenic F1 parent containing the PsMTA gene under the control of a CaMV 35S promoter, 75% of individuals accumulated more Cu (several-fold in some plants) than untransformed, control plants. These data suggest that PsMTA protein binds Cu in planta and that uncoupled (constitutive) expression of the PsMTA gene causes enhanced Cu accumulation. Roots of P. sativum plants grown under conditions of low Fe availability showed elevated activity of root surface Fe(III) reductase and accumulated more Cu than roots of plants grown in an Fe-supplemented solution. Changes in the expression of MT-like genes, coincident with changes in Fe availability, are consistent with a role in Cu homoeostasis.

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“…metabolic poisons for both plants and animals (Fleischer et al 1974). In higher plants, there is another thiol molecule possessing heavy metal-binding activity, poly(␥-glutamylcysteinyl)glycine, often called phytochelatin, which was first found in yeast (Murasugi et al 1981, Kondo et al 1985. Phytochelatin is synthesized by ␥-glutamylcysteine dipeptidyl transpeptidase with glutathione as a precursor (Grill et al 1989, Hayashi et al 1991, and it is induced after treatment with various heavy metals (Grill et al 1985(Grill et al , 1989.…”

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HEAVY‐METAL INDUCED CHANGES IN NONPROTEINACEOUS THIOL LEVELS AND HEAVY‐METAL BINDING PEPTIDE IN TETRASELMIS TETRATHELE (PRASINOPHYCEAE)

Satoh

Karaki

Kakehashi

et al. 1999

Journal of Phycology

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The effects of mercury and cadmium on the intracellular level of nonproteinaceous thiols in a unicellular green alga Tetraselmis tetrathele (West) Butcher (Prasinophyceae) were investigated by using a fluorescent dye, 5‐chloromethylfluorescein (5CMF), as a probe for nonproteinaceous thiols. The 5CMF fluorescence was observed in cytoplasm, and the intensity of the fluorescence was decreased by exposure of the cells to HgCl2. Analysis of the fluorescent intensity of 5CMF by flow cytometry made it possible to distinguish cells in three states during the dying process caused by HgCl2: a normal state, a thiol‐depleted state, and a dead state. Depletion of nonproteinaceous thiols began within 30 min, and they were completely depleted at 2 h. Most cells died after 24 h of exposure to more than 3.0 μM HgCl2, whereas exposure up to 1.0 mM CdCl2 did not cause depletion of nonproteinaceous thiols or cell death within 48 h. HPLC analyses revealed that glutathione was a major nonprotein thiol in T. tetrathele and that it was oxidized by exposing the cells to HgCl2. Phytochelatins, which play a great role in the tolerance to heavy metals of higher plants and many algae, could not be found in T. tetrathele. However, a tripeptide, Arg‐Arg‐Glu, was found to be abundant, and it showed ability to bind Hg2+, suggesting that it functions to scavenge heavy metals as well as thiol molecules.

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Synthesis of Metallothionein-like Peptides Cadystin A and B Occurring in a Fission Yeast, and Their Isomers

Cited by 13 publications

References 5 publications

Expression of the type 2 metallothionein-like gene MT2 from Arabidopsis thaliana in Zn2+-metallothionein-deficient Synechococcus PCC 7942: putative role for MT2 in Zn2+ metabolism

Expression of the type 2 metallothionein-like gene MT2 from Arabidopsis thaliana in Zn2+-metallothionein-deficient Synechococcus PCC 7942: putative role for MT2 in Zn2+ metabolism

Expression of the pea metallothionein-like gene PsMT A in Escherichia coli and Arabidopsis thaliana and analysis of trace metal ion accumulation: Implications for PsMT A function

HEAVY‐METAL INDUCED CHANGES IN NONPROTEINACEOUS THIOL LEVELS AND HEAVY‐METAL BINDING PEPTIDE IN TETRASELMIS TETRATHELE (PRASINOPHYCEAE)

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