Circular dichroism, kinetic and mass spectrometric studies of copper(I) and mercury(II) binding to metallothionein

Stillman, Martin J.; Thomas, D.K.; Trevithick, C.C.; Guo, Xuejiao; Siu, Michael

doi:10.1016/s0162-0134(99)00174-9

Cited by 44 publications

(26 citation statements)

References 34 publications

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“…Recently, electrospray MS has been used to study a number of metalcontaining MTs, 26 -32 including zinc-metallothionein, 26,27 cadmium-metallothionein, 26 -28 copper-metallothionein 29,30 and mercury-metallothionein. 29 In the present study, we developed nESI tandem quadrupole time-of-flight (Q-TOF) MS and inductively coupled plasma (ICP) MS techniques to study metal-protein interactions. We investigated the interactions of cisplatin with a zinc-and cadmium-bound native rabbit MT.…”

Section: Environment Biology and Toxicologymentioning

confidence: 99%

Direct evidence for co‐binding of cisplatin and cadmium to a native zinc‐ and cadmium‐containing metallothionein

Mandal¹,

Jiang²,

Li³

2003

Applied Organom Chemis

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Cisplatin is widely used to treat a number of cancers, and its covalent binding to DNA is believed to cause cell death; however, the roles of cisplatin-protein interactions in the mechanisms of action, toxicity, and resistance of the drug largely remain to be elucidated. Here, we investigate the interactions of cisplatin and a native rabbit metallothionein (MT), containing 1.4% zinc and 7.9% cadmium, using nanospray tandem quadrupole time-of-flight mass spectrometry (MS) and size-exclusion high-performance liquid chromatography with inductively coupled plasma MS. At near-neutral pH conditions, reactions between cisplatin and MT resulted in the formation of complexes that contained Cd 4 -Pt n -MT (n = 1-7). While zinc was displaced by cisplatin, both platinum and cadmium were bound to the same MT molecule. This is the first report to provide direct evidence for the co-binding of cadmium and platinum to MT, which suggests that the mechanism of the binding of cisplatin to the native MT may not be through the displacement of cadmium as previously proposed. A tandem MS investigation into the binding sites of the platinum and cadmium to MT showed platinum-and cadmium-related fragments, such as (PtS 2 C 2 H 7 N) + and (CdS 3 C 5 H 17 N 2 ) + , demonstrating the platinum-cysteine and cadmium-cysteine binding. In addition, detection of Cd 4 -Pt 7 -MT demonstrated more than ten metals bound to a single MT molecule. This finding was extended to the binding of MT with a five-fold excess of CdCl 2 . As many as 14 metal atoms (13 cadmium and one zinc) were detected bound to a single MT molecule, the complexes being Cd x -Zn-MT (x = 5-13). The high binding capacity of MT for cadmium and platinum is consistent with the role of MT in reduction of metal toxicity and its involvement in drug resistance.

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Section: Environment Biology and Toxicologymentioning

confidence: 99%

Direct evidence for co‐binding of cisplatin and cadmium to a native zinc‐ and cadmium‐containing metallothionein

Mandal¹,

Jiang²,

Li³

2003

Applied Organom Chemis

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“…The high affinity between mercury and thiolate (-SH) is the main reason why mercury is a strong poison to human 20 Conversely, the high affinity of mercury with -SH is one of the most important means to detoxify mercury, because the binding of Hg-SH in MT is one of the most important routes for mercury excretion. 23,24 The MT contents in each organ of the different rat groups shown in Table 3 indicate that large amounts of MT were induced in the liver and kidney of the cinnabar group IV and HgCl 2 group, in which the high contents of mercury in the two organs were observed in Table 2.…”

Section: Mt Concentrations In Rat Tissuesmentioning

confidence: 94%

“…Rats were maintained in air-conditioned metabolic boxes in standard conditions (18)(19)(20)(21)(22)(23)(24) • C) on a 12 h/12 h light/darkness cycle. They were randomly divided into six groups, with 10 rats in each group.…”

Section: Animal Treatmentmentioning

confidence: 99%

Metallothionein as a biomarker for mercury in tissues of rat fed orally with cinnabar

Huang

Shen

Zhuang

et al. 2004

Applied Organom Chemis

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Cinnabar, as one of the most widely used mineral drugs in traditional Chinese medicines, has been proven to have prominent curative effects in clinical use for more than 2000 years. But the safety and toxicity of the drug has been under constant debate in clinic usage. Metallothionein (MT) contains about 30% of cysteine in the molecule, and plays an important detoxification role against heavy metals. In this study, it was used as a biomarker to assess mercurial accumulation in rats fed orally with cinnabar. After feeding rats with cinnabar by gastric gavage at different dosages and at different times, the distribution of heavy metals (including mercury, copper and zinc) and MT was investigated among rat tissues, including liver, kidney, heart, brain, testis and blood. Metals and MT determinations were carried out using inductively coupled plasma mass spectrometry (ICP-MS) and a modified mercury saturation assay technique respectively. The results indicated that mercury was easily accumulated in the tissues of rats exposed to cinnabar, especially in kidney. For example: at a feeding dosage of 5 g kg −1 (bw) for 4 weeks, the mercury concentrations in kidney were 13, 8.7, 21.6 and 26 times those in liver, testis, brain and heart respectively; and at 2.5 g kg −1 (bw) for 2 weeks, the mercury concentrations in kidney were 21, 2.1, 3 and 21 times those in liver, testis, brain and heart respectively. In addition, mercury in kidney and liver of all cinnabar groups was significantly higher than that of the control group (P < 0.01). A high positive correlation observed between MT concentrations and mercury levels in both liver and kidney (R 2 = 0.9299, P < 0.02 for liver; R 2 = 0.9923, P < 0.0008 for kidney) indicated that MT could be used as a biomarker for mercury in tissues.

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“…6 is relatively difficult because of the complexity of the clusters of peaks observed (mercury, mercury-copper, and mercury-zinc may co-exist) and the strong binding between mercury, copper and MT which made it difficult to de-metal by acidification to form apo-MT that can be easily identified with ESI-MS. 25 To interpret the MT isoforms and subisoforms of rat kidney from the mass spectra in the vicinity of the TIC, the masses found were compared with the theoretical values calculated by the masses of apo-MT reported in rat tissues and the tentative masses of binding metals in the formula. 18,26 The tentative formulas of the MT isoforms and subisoforms corresponding to the masses found from the mass spectra are listed in Table 2.…”

Section: Rp Hplc-esi-ms Detectionmentioning

confidence: 99%

Investigation of mercury metallothionein complexes in tissues of rat after oral intake of HgCl2

Shen

Huang

Zhuang

et al. 2005

Appl. Organometal. Chem.

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Mercury, a highly toxic metal found widely throughout the environment, is a potent inducer of metallothionein (MT) expression. The role of MTs in the detoxification of mercury after its oral intake in mammals is studied. After feeding rats with mercuric chloride by gastric gavage, the distribution of heavy metals in rat tissues was investigated by inductively coupled plasma mass spectrometry (ICP-MS). Extensive accumulation of mercury, copper and zinc in kidney and liver is observed. A homemade preparative size-exclusion chromatography (SEC) column (30cm x 1.9cm) packed with Sephadex G-75 (40-120 mum particle size) gel (Pharmacia) was used for the purification of NIT fractions in rat tissues. Preliminary results from SEC indicate that the mercury-binding MT levels in liver were much lower than in kidney. The NIT fractions were collected, desalted, and then separated by reversed-phase high-performance liquid chromatography (HPLC) with UV-Vis spectrometry, ICP-MS and electrospray ionization MS detection. One major and several minor peaks were observed in the HPLC chromatograms of the MT fraction for the kidney sample. UV absorption spectra indicate that MTs were found to bind with mercury. There were no significant mercury-binding MTs detected in the liver sample using UV detection. ICP-MS detection showed that mercury-binding MTs in kidney contained large amounts of mercury and copper but little zinc. Further characterization with ESI-MS showed that the major peak found in kidney contained Hg6Cu, Hg5Cu2-MT-2c and Hg-6-MT-2beta, Hg6Cu-MT-1gamma, Hg-7-MT-2alpha. However, distinction between copper and zinc could not be made based on current mass spectrometric analysis because of instrumental resolution limitations. Copyright (C) 2004 John Wiley Sons, Ltd

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Circular dichroism, kinetic and mass spectrometric studies of copper(I) and mercury(II) binding to metallothionein

Cited by 44 publications

References 34 publications

Direct evidence for co‐binding of cisplatin and cadmium to a native zinc‐ and cadmium‐containing metallothionein

Direct evidence for co‐binding of cisplatin and cadmium to a native zinc‐ and cadmium‐containing metallothionein

Metallothionein as a biomarker for mercury in tissues of rat fed orally with cinnabar

Investigation of mercury metallothionein complexes in tissues of rat after oral intake of HgCl2

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