Some Metal Complexes of Sulfur-containing Amino Acids<sup>1,2</sup>

Li, Norman C.; Manning, Richard A.

doi:10.1021/ja01625a006

Cited by 172 publications

(77 citation statements)

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“…We point out that, if Hg-or Ag:(y-GluCys)n-Gly mercaptide complexes are formed in vivo, then, owing to their stability, they would probably escape detection by standard methods that detect GSH and phytochelatins on the basis of reactive sulfhydryl groups (see GSH assay in "Materials and Methods"). Because Cd-GSH complexes are many orders of magnitude less stable than Ag-or Hg-GSH complexes (4,22,35), it is interesting to speculate that the unique potency of Cd>2 as an inducer of phytochelatin synthesis and accumulation may reflect an evolutionary adaptation of the organism to the inability of GSH to effectively bind Cd>2 ions with the stability required for Cd24 detoxification. In support of this idea is the fact that the affinity of Cd>2 to ('y-Glu-Cys)n-Gly peptides of length n = 1 (GSH), 2, and 3 increases significantly with increasing peptide length (14).…”

Section: Competition Between Ag+ and Cu2+mentioning

confidence: 99%

Heavy Metal-Activated Synthesis of Peptides in Chlamydomonas reinhardtii

Howe¹,

Merchant²

1992

Plant Physiol.

144

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In this study, we have addressed the capacity of the green alga Chiamydomonas reinhardtii to produce metal-binding peptides in response to stress induced by the heavy metals Cd2 , Hg2+, and Ag+. Cells cultured in the presence of sublethal concentrations of Cd2+ synthesized and accumulated oligopeptides consisting solely of glutamic acid, cysteine, and glycine in an average ratio of 3:3:1. Cadmium-induced peptides were isolated in their native form as higher molecular weight peptide-metal complexes with an apparent molecular weight of approximately 6.5 x 103. The isolated complex bound cadmium (as evidenced by absorption spectroscopy) and sequestered (with a stoichiometry of 0.7 moles of cadmium per mole of cysteine) up to 70% of the total cadmium found in extracts of cadmium-treated cells. In Hg2+-treated cells, the principal thiol-containing compound induced by Hg2 ions was glutathione. It is possible that glutathione functions in plant cells (as it does in animal cells) to detoxify heavy metals. Cells treated with Ag+ ions also synthesized a sulfur-containing component with a charge to mass ratio similar to Cd2+-induced peptides. But, in contrast to the results obtained using Cd2 as an inducer, these molecules did not accumulate to significant levels in Ag+-treated cells. The presence of physiological concentrations of Cu2+ in the growth medium blocked the synthesis of the Ag+-inducible component(s) and rendered cells resistant to the toxic effects of Ag+, suggesting competition between Cu2+ and Ag+ ions, possibly at the level of metal uptake.Many organisms respond to the cytotoxic effects of heavy metals by synthesizing metal-chelating proteins or peptides. The predominant class of such molecules in plants, algae, and some fungi are the small, cysteine-rich peptides referred to as phytochelatins (12), Cd2+-binding peptides (25), cadystins (19), or -y-glutamyl peptides (29). These molecules have the general structure (,y-Glu-Cys)n-Gly (12,17,20,34), where n can range from 2 to 11 depending on the species from which the peptides are isolated and the conditions of their induction (10,13 tionally activated, metal-dependent, enzymatic pathway from precursor GSH (13,30,31,34). This view is supported by genetic evidence showing that yeast cells with defects in the GSH biosynthetic pathway fail to accumulate phytochelatins in response to heavy metal stress (26). Elucidation of the pathway for the biosynthesis of phytochelatins in vascular plants has recently culminated with the identification of a "phytochelatin synthase" activity in suspension cultures of Silene cucubalus (1 1). The isolated enzyme has a heavy metaldependent y-glutamylcysteine dipeptidyl transpeptidase activity that is proposed to be responsible for the metal-regulated biosynthesis of phytochelatins in vivo. The further characterization of phytochelatin synthase will provide a focal point for the study of the biosynthetic regulation and physiological function(s) of these novel peptides.The phytochelatin response pathway in plants presumably ...

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Section: Competition Between Ag+ and Cu2+mentioning

confidence: 99%

Heavy Metal-Activated Synthesis of Peptides in Chlamydomonas reinhardtii

Howe¹,

Merchant²

1992

Plant Physiol.

144

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“…There are several preparative and spectro-scopic studies concerning metal complexes of sulphurcontaining amino-acids (e.g. Li & Manning, 1955;Lenz & Martell, 1964;Shindo & Brown, 1965;McAuliffe, Quagliano & Vallarino, 1966;Livingstone & Nolan, 1968) which show that these ligands can play different roles in the different cases as they have three points for coordination to metal. In the present report the results of the structure analysis of dichloro-(Smethyl-L-cysteine)palladium(I I) monohydrate are given, which show that S-methyl-L-cysteine behaves as a bidentate ligand coordinating through sulphur and nitrogen to palladium.…”

Section: Introductionmentioning

confidence: 99%

The crystal and molecular structure of dichloro(S-methyl-L-cysteine)palladium(II) monohydrate

Battaglia¹,

Corradi²,

Palmieri³

et al. 1973

Acta Crystallogr Sect B

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“…(g) Grenthe 1962 (c) Li and Manning 1955 (h) Bear et al 1962 (d) Nourmand and Meissami 1982 (i) Nourrnand and Meissami 1983 (e) Cefola et al 1962 3.2 BatchContactTesting…”

Section: Selectionof Candidatemoleculesfor Selectivemercurycomplexationmentioning

confidence: 99%