Metal donation and apo-metalloenzyme activation by stable isotopically labeled metallothionein

Mason, Andrew Z.; Perico, Natalie; Moeller, Rhonda; Thrippleton, Kelly; Potter, Tiffany; Lloyd, D.

doi:10.1016/j.marenvres.2004.03.082

Cited by 29 publications

(32 citation statements)

References 9 publications

(5 reference statements)

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“…It has been described that Zn bound to MT’s seven Zn binding sites are donated to other acceptor proteins in a fixed, predetermined order 50 , 51 . Given the likely role of MT as a Zn reservoir, 38 , 52 , 53 it is uncertain what the net effect of Zn displacement from MT in combination with increased MT expression on the intracellular distribution and availability of Zn will be. It has been reported that Zn is displaced by Cd from MT in a similar, predetermined order, with the lower affinity Zn atoms displaced first 7 , 48 .…”

Section: Discussionmentioning

confidence: 99%

Accumulation of cadmium in insulin-producing β cells

Muayed¹,

Raja

Zhang

et al. 2012

Islets

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Evidence suggests that chronic low level cadmium exposure impairs the function of insulin-producing β cells and may be associated with type-2 diabetes mellitus. Herein, we describe the cadmium content in primary human islets and define the uptake kinetics and effects of environmentally relevant cadmium concentrations in cultured β cells. The average cadmium content in islets from 10 non-diabetic human subjects was 29 ± 7 nmol/g protein (range 7 to 72 nmol/g protein). Exposure of the β-cell line MIN6 to CdCl2 concentrations between 0.1 and 1.0 µmol/L resulted in a dose- and time-dependent uptake of cadmium over 72 h. This uptake resulted in an induction of metallthionein expression, likely enhancing cellular cadmium accumulation. Furthermore, cadmium accumulation resulted in an inhibition of glucose stimulated insulin secretion in MIN6 cells and primary mouse islets. Our results indicate that this impairment in β-cell function is not due to an increase in cell death or due to an increase in oxidative stress. We conclude that mouse β cells accumulate cadmium in a dose- and time-dependent manner over a prolonged time course at environmentally relevant concentrations. This uptake leads to a functional impairment of β-cell function without significant alterations in cell viability, expression of genes important for β-cell function or increase in oxidative stress.

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Section: Discussionmentioning

confidence: 99%

Accumulation of cadmium in insulin-producing β cells

Muayed¹,

Raja

Zhang

et al. 2012

Islets

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“…Oxidation would rapidly result. 14, 15,17,42 The conundrum is thus how the Zn 2+ ions bound in MT transfer to apoenzymes with lower binding affinities without destroying the MT that still has six Zn 2+ ions bound and why such a disastrous consequence would be a property of MT.…”

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confidence: 99%

Single-Domain Metallothioneins: Evidence of the Onset of Clustered Metal Binding Domains in Zn-rhMT 1a

2013

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Mammalian metallothioneins bind up to seven Zn(2+) ions in two distinct domains: an N-terminal β-domain that binds three Zn(2+) ions and a C-terminal α-domain that binds four Zn(2+) ions. Domain specificity has been invoked in the metalation mechanism with cluster formation and bridging of the 20 Cys residues taking place prior to saturation with seven Zn(2+) ions. We report a novel experiment that examines Zn(2+) metalation by exploiting the expected decrease in K(F) at the onset of clustering using electrospray ionization mass spectrometry (ESI-MS). During the titration with Zn(2+), the ESI-MS data show that several metalated species coexist until the fully saturated proteins are formed. The relative Zn binding affinities of the seven total sites in the α- and β-fragments were determined through direct competition for added Zn(2+). The K(F) values for each Zn(2+) are expected to decrease as a function of the remaining available sites and the onset of clustering. Analysis shows that Zn(2+) binds to β-rhMT with a greater affinity than α-rhMT. The incremental distribution of Zn(2+) between the competing fragments and apo-βα-rhMT (essentially three and four sites competing with seven sites) identifies the exact point at which clustering begins in the full protein. Analysis of the speciation data shows that Zn(5)-MT forms before clustering begins. This means that all 20 Cys residues of apo-βα-rhMT are bound terminally to Zn(2+) as [Zn(Cys)(4)](2-) units before clustering begins; there is no domain preference in this first metalation stage. Preferential binding of Zn(2+) to β- and α-rhMT at the point where βα-rhMT must form clusters is caused by a significant decrease in the affinity of βα-rhMT for further Zn(2+). The single-domain Zn(5)-rhMT, in which there are no exposed cysteine sulfurs, is a key component of the metalation pathway because the lower affinities of the two clustered Zn(2+) ions allow donation to apoenzymes.

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“…27 The isotopic specificity of ICP MS encourages studies aimed at the identification of molecules acting as metal donors to various enzymes. 28 ICP MS detectable elements in proteins and protein complexes can be of multifarious origin (Fig. 1).…”

Section: Protein Researchmentioning

confidence: 99%

“…156 An innovative methodology based on ion-exchange HPLC-ICP MS was developed to study the ability of metallothionein to donate essential and non-essential metals to apo-carbonic anhydrase. 28 Stable isotopically labeled 67 Zn 3 Cd 4 -MT-II was used to differentiate between the Zn donated from MT-II and that from extraneous sources. 28 6.1.2.…”

Section: Icp Ms Related Techniquesmentioning

confidence: 99%

Advances in analytical methodology for bioinorganic speciation analysis: metallomics, metalloproteomics and heteroatom-tagged proteomics and metabolomics

Szpunar

2005

Analyst

372

284

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The recent developments in analytical techniques capable of providing information on the identity and quantity of heteroatom-containing biomolecules are critically discussed. Particular attention is paid to the emerging areas of bioinorganic analysis including: (i) a comprehensive analysis of the entirety of metal and metalloid species within a cell or tissue type (metallomics), (ii) the study of the part of the metallome involving the protein ligands (metalloproteomics), and (iii) the use of a heteroelement, naturally present in a protein or introduced in a tag added by means of derivatisation, for the spotting and quantification of proteins (heteroatom-tagged proteomics). Inductively coupled plasma mass spectrometry (ICP MS), used as detector in chromatography and electrophoresis, and supported by electrospray and MALDI MS, appears as the linchpin analytical technique for these emerging areas. This review focuses on the recent advances in ICP MS in biological speciation analysis including sensitive detection of non-metals, especially of sulfur and phosphorus, couplings to capillary and nanoflow HPLC and capillary electrophoresis, laser ablation ICP MS detection of proteins in gel electrophoresis, and isotope dilution quantification of biomolecules. The paper can be considered as a followup of a previous review by the author on a similar topic (J. Szpunar, Analyst, 2000, 125, 963).

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Metal donation and apo-metalloenzyme activation by stable isotopically labeled metallothionein

Cited by 29 publications

References 9 publications

Accumulation of cadmium in insulin-producing β cells

Accumulation of cadmium in insulin-producing β cells

Single-Domain Metallothioneins: Evidence of the Onset of Clustered Metal Binding Domains in Zn-rhMT 1a

Advances in analytical methodology for bioinorganic speciation analysis: metallomics, metalloproteomics and heteroatom-tagged proteomics and metabolomics

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