共查询到20条相似文献,搜索用时 31 毫秒
1.
Metallothionein (MT) is a ubiquitous mammalian protein comprising 61 or 62 nonaromatic amino acids of which 20 are cysteine residues. The high sulfhydryl content imparts to this protein a unique and remarkable ability to bind multiple metal ions in structurally significant metal–thiolate clusters. MT can bind seven divalent metal ions per protein molecule in two domains with exclusive tetrahedral metal coordination. The domain stoichiometries for the M7S20 structure are M4(Scys)11 (α domain) and M3(Scys)9 (β domain). Up to 12 Cu(I) ions can displace the 7 Zn2+ ions bound per molecule in Zn7–MT. The incoming Cu(I) ions adopt a trigonal planar geometry with domain stoichiometries for the Cu12S20 structure of Cu6(Scys)11 and Cu6(Scys)9 for the α and β domains, respectively. The circular dichroism (CD) spectra recorded as Cu+ is added to Zn7–MT to form Cu12–MT directly report structural changes that take place in the metal binding region. The spectrum arises under charge transfer transitions between the cysteine S and the Cu(I); because the Cu(I)–thiolate cluster units are located within the chiral binding site, intensities in the CD spectrum are directly related to changes in the binding site. The CD technique clearly indicates stoichiometries of several Cu(I)–MT species. Model Cu(I)–thiolate complexes, using the tripeptide glutathione as the sulfhydryl source, were examined by CD spectroscopy to obtain transition energies and the Cu(I)–thiolate coordination geometries which correspond to these bands. Possible structures for the Cu(I)–thiolate clusters in the α and β domains of Cu12–MT are proposed. © 1994 Wiley-Liss, Inc. 相似文献
2.
Montserrat Serra-Batiste Neus Cols Luis A. Alcaraz Antonio Donaire Pilar González-Duarte Milan Vašák 《Journal of biological inorganic chemistry》2010,15(5):759-776
Most crustacean metallothioneins (MTs) contain 18 Cys residues and bind six divalent metal ions. The copper-specific CuMT-2
(MTC) of the blue crab Callinectes sapidus with 21 Cys residues, of which six are organized in two uncommon Cys-Cys-Cys sequences, represents an exception. However,
its metal-binding properties are unknown. By spectroscopic and spectrometric techniques we show that all 21 Cys residues of
recombinant MTC participate in the binding of Cu(I), Zn(II), and Cd(II) ions, indicating that both Cys triplets act as ligands.
The fully metallated M8
II–MTC (M is Zn, Cd) form possesses high- and low-affinity metal binding sites, as evidenced by the formation of Zn6–MTC and Cd7–MTC species from M8
II–MTC after treatment with Chelex 100. The NMR characterization of Cd7–MTC suggests the presence of a two-domain structure, each domain containing one Cys triplet and encompassing either the three-metal
or the four-metal thiolate cluster. Whereas the metal–Cys connectivities in the three-metal cluster located in the N-terminal
domain (residues 1–31) reveal a Cd3Cys9 cyclohexane-like structure, the presence of dynamic processes in the C-terminal domain (residues 32–64) precluded the determination
of the organization of the four-metal cluster. Absorption and circular dichroism features accompanying the stepwise binding
of Cu(I) to MTC suggest that all 21 Cys are involved in the binding of eight to nine Cu(I) ions (Cu8–9–MTC). The subsequent generation of Cu12–MTC involves structural changes consistent with a decrease in the Cu(I) coordination number. Overall, the metal-binding properties
of MTC reported here contribute to a better understanding of the role of Cys triplets in MTs. 相似文献
3.
4.
Roger Miras Isabelle Morin Florent Guillain Elisabeth Mintz 《Journal of biological inorganic chemistry》2008,13(2):195-205
Copper is both an essential element as a catalytic cofactor and a toxic element because of its redox properties. Once in the
cell, Cu(I) binds to glutathione (GSH) and various thiol-rich proteins that sequester and/or exchange copper with other intracellular
components. Among them, the Cu(I) chaperone Atx1 is known to deliver Cu(I) to Ccc2, the Golgi Cu–ATPase, in yeast. However,
the mechanism for Cu(I) incorporation into Atx1 has not yet been unraveled. We investigated here a possible role of GSH in
Cu(I) binding to Atx1. Yeast Atx1 was expressed in Escherichia coli and purified to study its ability to bind Cu(I). We found that with an excess of GSH [at least two GSH/Cu(I)], Atx1 formed
a Cu(I)-bridged dimer of high affinity for Cu(I), containing two Cu(I) and two GSH, whereas no dimer was observed in the absence
of GSH. The stability constants (log β) of the Cu(I) complexes measured at pH 6 were 15–16 and 49–50 for CuAtx1 and Cu2I(GS−)2(Atx1)2, respectively. Hence, these results suggest that in vivo the high GSH concentration favors Atx1 dimerization and that Cu2I(GS−)2(Atx1)2 is the major conformation of Atx1 in the cytosol. 相似文献
5.
Copper and other transition metal ions and their complexes are catalysts for the decomposition of nitrosothiols. In this
way they catalyze the biological functions of nitrosothiols. The kinetics and mechanism of the reaction of two nitrosothiols,
S-nitrosothiolactic acid and S-nitrosoglutathione (GSNO), with copper(I) are reported. The kinetics of the reaction of Cu(MeCN)
n
+ (n=0–3) with the nitrosothiols were studied. The results indicate that Cu+
aq is the active species in the GSNO system, with k(Cu+
aq+GSNO)=(9.4 ±2.0)×107 dm3 mol−1 s−1 . The results also indicate that the Cu(MeCN)
n
+ (n=0–3) complexes react with S-nitrosothiolactic acid. Transient species are formed in these processes. The results suggest that these species contain copper(I)
and thiol. The results shed light on the catalytic role of copper complexes in the decomposition of S-nitrosothiols.
Received 10 April 1999 / Accepted 17 December 1999 相似文献
6.
Maria T. Salgado Kristy L. Bacher Martin J. Stillman 《Journal of biological inorganic chemistry》2007,12(3):294-312
Steady-state emission spectra, excited-state lifetimes, kinetic data, and mass spectroscopic properties are reported for Ag(I)-
and mixed Ag(I)/Cu(I)-substituted α and β domains of recombinant human metallothionein (MT1a). Kinetic analysis of the changes
in the Cu(I) emission spectra during the stepwise displacement of Cu(I) ions by Ag(I) at room temperature shows that the rate
of displacement of Cu(I) is unexpectedly slow. Although the first Ag(I) added results in major changes in the Cu(I)-MT binding
site, Cu(I) displacement by Ag(I) does not take place until the addition of the third Ag(I), and is completed by the addition
of the seventh Ag(I). The emission from Ag(I) and mixed Cu(I)/Ag(I)-MT species at 77 K shows that the band maxima shift as
a function of Ag(I) loading, which can be correlated with shifts in coordination geometry from trigonal to digonal. Two phosphorescence
lifetimes were detected for the Ag(I)-substituted α and β domains of MT, which are attributed to the presence of Ag(I) ions
in two different environments. The lifetime of Ag(I)-substituted MT was found to be shorter when the Ag(I)-MT species were
formed by Ag(I) additions to the Cu(I)-substituted α and β fragments than when the Ag(I)-MT species were formed from the apo-α
and apo-β fragments, suggesting the formation of structurally different Ag(I)-MT clusters. Electrospray ionization mass spectrometric
studies suggest the metallation reactions of Ag(I) with MT take place in a series of steps to form a series of Ag(I)-substituted
MT species. Ag(I)-substituted MT species are not detected until past the addition of 3 mol equiv of Ag(I), suggesting that
cluster formation begins only at this point, stabilizing the metallated species sufficiently to survive ionization. 相似文献
7.
David Poger Clara Fillaux Roger Miras Serge Crouzy Pascale Delangle Elisabeth Mintz Christophe Den Auwer Michel Ferrand 《Journal of biological inorganic chemistry》2008,13(8):1239-1248
X-ray absorption techniques have been used to characterise the primary coordination sphere of Cu(I) bound to glutathionate
(GS−), to Atx1 and in Cu2I(GS−)2(Atx1)2, a complex recently proposed as the major form of Atx1 in the cytosol. In each complex, Cu(I) was shown to be triply coordinated.
When only glutathione is provided, each Cu(I) is triply coordinated by sulphur atoms in the binuclear complex CuI
2(GS−)5, involving bridging and terminal thiolates. In the presence of Atx1 and excess of glutathione, under conditions where CuI
2(GS−)2(Atx1)2 is formed, each Cu(I) is triply coordinated by sulphur atoms. Given these constraints, there are two different ways for Cu(I)
to bridge the Atx1 dimer: either both Cu(I) ions contribute to bridging the dimer, or only one Cu(I) ion is responsible for
bridging, the other one being coordinated to two glutathione molecules. These two models are discussed as regards Cu(I) transfer
to Ccc2a.
相似文献
Serge CrouzyEmail: |
8.
The disproportionation reaction between the copper(II) complexes, Cu(ClO4)2 · 6H2O and [Cu(S2CNR2)2] is a well-established route to copper(III) complexes [Cu(S2CNR2)2][ClO4] but to date the nature of the copper(I) species generated has remained a mystery. We now show that with [Cu(S2CNPr2)2] this is the copper(I) cluster, [Cu8(μ2,μ2-S2CNPr2)6][ClO4]2, which contains a cubic array of copper atoms, each face cube being capped by a dithiocarbamate ligand such that the sulfur atoms define an icosahedron and the backbone carbons an octahedron around the cube centroid. A crystal structure of [Cu4(μ2,η1-S2CNBu2)4] is also presented for comparison. 相似文献
9.
C. Immoos Michael G. Hill Donita Sanders James A. Fee Claire E. Slutter John H. Richards Harry B. Gray 《Journal of biological inorganic chemistry》1996,1(6):529-531
The electrochemistry of a water-soluble fragment from the CuA domain of Thermus thermophilus cytochrome ba
3
has been investigated. At 25 °C, CuA exhibits a reversible reduction at a pyridine-4-aldehydesemicarbazone-modified gold electrode (0.1 M Tris, pH 8) with E° = 0.24 V vs NHE. Thermodynamic parameters for the [Cu(Cys)2Cu]+/0 electrode reaction were determined by variable-temperature electrochemistry (ΔS°rc = –5.4(12) eu, ΔS° = –21.0(12) eu, ΔH° = –11.9(4) kcal/mol;ΔG° = –5.6 (11) kcal/mol). The relatively small reaction entropy is consistent with a low reorganization energy for [Cu(Cys)2Cu]+/0 electron transfer. An irreversible oxidation of [Cu(Cys)2Cu]+ at 1 V vs NHE confirms that the CuII:CuII state of CuA is significantly destabilized relative to the CuII state of analogous blue-copper proteins.
Received: 3 June 1996 / Accepted: 26 August 1996 相似文献
10.
Zhi-Chun Ding Qi Zheng Bin Cai Wen-Hao Yu Xin-Chen Teng Yang Wang Guo-Ming Zhou Hou-Ming Wu Hong-Zhe Sun Ming-Jie Zhang Zhong-Xian Huang 《Journal of biological inorganic chemistry》2007,12(8):1173-1179
Human metallothionein-3 (hMT3), also named human neuronal growth inhibitory factor (hGIF), is attractive due to its distinct
neuronal growth inhibitory activity, which is not shown by other human MT isoforms. It has been reported that the neuronal
growth inhibitory activity arises from the N-terminal β-domain rather than its C-terminal α-domain. However, previous bioassay
results have shown that the single β-domain is less effective at inhibiting the neuron growth than that in intact hMT3 on
a molar basis, which suggests that the α-domain is indispensable to the neuronal growth inhibitory activity of hMT3. In order
to confirm this assumption, we constructed two domain-hybrid mutants, the β(MT3)–β(MT3) mutant and the β(MT3)–α(MT1) mutant,
and investigated their structural and metal binding properties by UV-vis spectroscopy, CD spectroscopy, pH titration, DTNB
reaction, EDTA reaction, etc. The results showed that stability of the Cd3S9 cluster of the β(MT3)–β(MT3) mutant decreased significantly while the Cd3S9 cluster of the β(MT3)–α(MT1) mutant had a similar stability and solvent accessibility to that of hMT3. Interestingly, the
bioassay results showed that the neuronal growth inhibitory activity of the β(MT3)–β(MT3) mutant decreased significantly,
while the β(MT3)–α(MT1) mutant showed similar inhibitory activity to hMT3. Based on these results, we conclude that the α-domain
is indispensable and plays an important role in modulating the stability of the metal cluster in the β-domain by domain–domain
interactions, thus influencing the bioactivity of hMT3.
Z.-C. Ding and Q. Zheng contributed equally to this work. 相似文献
11.
Complex pbt2Cu8Br12 [pbt=pyridine-2,6-diylbis(methyleneamino-TEMPO)] was synthesized from CuBr2 and a new ligand pbt, and characterized by means of X-ray crystal structure analysis and magnetic measurements. The centrosymmetric molecule consists of a Cu6Br10 cluster sandwiched with two pbt·CuBr complexes. Detailed geometrical analysis and magnetic analysis reveal the presence of four copper(I) and four copper(II) ions in a molecule. Antiferromagnetic couplings observed can be attributed to the intermolecular radical?radical and intramolecular copper(II)?copper(II) interactions. 相似文献
12.
The synthesis of an unsymmetrical phenanthroline-based ligand, 2-methyl-9-(3,5-dimethylpyrazolylmethyl)-1,10-phenanthroline (L), and its cupric [Cu(II)] (1) and cuprous [Cu(I)] (2) complexes, are reported. The X-ray structures of each of these Cu complexes show distinct changes in coordination environments consistent with the geometrical preferences of the two oxidation states. In the solid-state, the Cu(II) complex (1) adopts a geometry best described as trigonal bipyramidal, while the Cu(I) complex (2) consists of a single dicationic dimer in which the ligand bridges between two copper ions, separated by 4.26 Å. The two Cu(I) coordination sites differ in 2 with one copper center complexed in a trigonal planar geometry and the other copper in a distorted tetrahedral environment; the latter coordination results from an additional CH3CN ligand. Complex 1 exhibits a reversible redox process at −0.34 V versus Fc/Fc+ in CH3CN, attributable to the Cu2+/Cu+ couple, while the dimeric Cu(I) complex (2) does not display this redox couple on the CV timescale. Over minutes however, complex 1 does oxidize in the presence of dioxygen to 2 in CH3CN. 相似文献
13.
Corinna R. Hess Judith P. Klinman Ninian J. Blackburn 《Journal of biological inorganic chemistry》2010,15(8):1195-1207
Tyramine β-monooxygenase (TBM) is a member of a family of copper monooxygenases containing two noncoupled copper centers,
and includes peptidylglycine monooxygenase and dopamine β-monooxygenase. In its Cu(II) form, TBM is coordinated by two to
three His residues and one to two non-His O/N ligands consistent with a [CuM(His)2(OH2)2–CuH(His)3(OH2)] formulation. Reduction to the Cu(I) state causes a change in the X-ray absorption spectroscopy (XAS) spectrum, consistent
with a change to a [CuM(His)2S(Met)–CuH(His)3] environment. Lowering the pH to 4.0 results in a large increase in the intensity of the Cu(I)–S extended X-ray absorption
fine structure (EXAFS) component, suggesting a tighter Cu–S bond or the coordination of an additional sulfur donor. The XAS
spectra of three variants, where the CuM Met471 residue had been mutated to His, Cys, and Asp, were examined. Significant differences from the wild-type enzyme are
evident in the spectra of the reduced mutants. Although the side chains of His, Cys, and Asp are expected to substitute for
Met at the CuM site, the data showed identical spectra for all three reduced variants, with no evidence for coordination of residue 471.
Rather, the K-edge data suggested a modest decrease in coordination number, whereas the EXAFS indicated an average of two
His residues at each Cu(I) center. These data highlight the unique role of the Met residue at the CuM center, and pose interesting questions as to why replacement by the cuprophilic thiolate ligand leads to detectable activity
whereas replacement by imidazole generates inactive TBM. 相似文献
14.
The copper(II) complex with tolfenamic acid [Cu(tolf)2(H2O)]2 was studied by X-band and K-band EPR spectroscopies in the temperature range from 90 to 300 K. The Cu2+ ions in dinuclear complex show a strong antiferromagnetic exchange interaction with |J| = 292 cm−1. The EPR spectra, which were observed for [Cu(tolf)2(H2O)]2, are typical powder spectra of the copper pairs. The spectra exhibit the hyperfine structure in low temperature range. The values of the spin-Hamiltonian parameters were determined on the basis of the best fit for the simulated spectra at both K-band (0.75 cm−1) at T = 298 K and X-band (0.3 cm−1) at T = 93 K as compared with the experimentally observed spectra. These values show that the local environment around the copper species is distorted tetragonal pyramid. This EPR evidence is consistent with the crystallographic data. 相似文献
15.
Francesco Guerrieri Velia Minicozzi Silvia Morante Giancarlo Rossi Sara Furlan Giovanni La Penna 《Journal of biological inorganic chemistry》2009,14(3):361-374
The octarepeat region of the prion protein can bind Cu2+ ions up to full occupancy (one ion per octarepeat) at neutral pH. While crystallographic data show that the HGGG octarepeat
subdomain is the basic binding unit, multiple histidine coordination at lower Cu occupancy has been reported by X-ray absorption
spectroscopy, EPR, and potentiometric experiments. In this paper we investigate, with first principles Car–Parrinello simulations,
the first step for the formation of the Cu low-level binding mode, where four histidine side chains are coordinated to the
same Cu2+ ion. This step involves the further binding of a second histidine to an already HGGG domain bonded Cu2+ ion. The influence of the pH on the ability of Cu to bind two histidine side chains was taken into account by simulating
different protonation states of the amide N atoms of the two glycines lying nearest to the first histidine. Multiple histidine
coordination is also seen to occur when glycine deprotonation occurs and the presence of the extra histidine stabilizes the
Cu–peptide complex. Though the stabilization effect slightly decreases with the number of deprotonated glycines (reaching
a minimum when both N atoms of the two nearest glycines are available as Cu ligands), the system is still capable of binding
the second histidine in a 4N tetrahedral (though slightly distorted) coordination, whose energy is very near to that of the
crystallographic square-planar 3N1O coordination. This result suggests that at low metal concentration the reorganization
energy associated with Cu(II)/Cu(I) reduction is small also at pH ~ 7, when glycines are deprotonated.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
相似文献
Giovanni La PennaEmail: |
16.
Scanning electrochemical microscopy (SECM) combined with surface plasmon resonance (SPR), SECM-SPR, was applied for real-time detection of the incorporation of Cu(2+) by apo-metallothionein (apo-MT) immobilized on the SPR substrate and release of Cu(2+) from surface-confined metallothionein (MT). Cu(2+) anodically stripped from a Cu-coated SECM Au tip was sequestered by apo-MT upon its diffusion to the SPR substrate, and release of Cu(2+) by MT was accomplished by generating protons via oxidation of hydroquinone at the tip. The high sensitivity of the SPR instrument is capable of following the structural and compositional changes of MT molecules during the metal sequestration and release processes. Due to the enhanced mass transfer rate at the SECM tip, the complication of mass transfer limitation on kinetic measurements, commonly encountered in flow injection SPR, is circumvented. The time-resolved SPR response reveals stepwise changes among three stable MT structures and allows the number of copper ions coordinated in each structure to be determined. The numbers of copper ions incorporated by each MT molecule in the three structures were determined to be 5, 9, and 12. This work expands the SECM-SPR approach to assessments of the dynamics and affinity of binding of small ions to surface-confined proteins and to studies of proteins that do not undergo facile electron transfer reactions. 相似文献
17.
Dacil Zurita Isabelle Gautier-Luneau Stéphane Ménage J.-L. Pierre Eric Saint-Aman 《Journal of biological inorganic chemistry》1997,2(1):46-55
Copper(II) complexes derived from the tripodal ligand bis(3′-t–butyl-2′-hydroxybenzyl)(2-pyridylmethyl)amine (LH2) have been studied in order to mimic the redox active site of the free radical-containing copper metalloenzyme galactose
oxidase. In non-coordinating solvents such as dichloromethane, only an EPR-silent dimeric complex was obtained (L2Cu2). The crystal structure of L2Cu2 revealed a "butterfly" design of the [Cu(μOR)2Cu] unit, which is not flattened and leads to a short Cu–Cu distance, the t–butyl groups being localized on the same side of the [Cu(μOR)2Cu] unit. The dimeric structure was broken down by acetonitrile or by alcohols, leading quantitatively to a brown mononuclear
copper(II) complex. UV-visible and EPR data indicated the coordination of the solvent in these mononuclear complexes. Electrochemical
as well as chemical (silver acetate) one-electron oxidation of acetonitrile solutions of the monomeric complex led to a yellow-green
solution. Based on EPR, UV-visible and resonance Raman spectroscopy, the one-electron oxidation product was identified as
a cupric phenoxyl radical system. It slowly decomposes into a product where the ligand has been substituted (dimerization)
in the para position of the hydroxyl group, for one of the phenolic groups. The data for the one-electron oxidized species provides strong
evidence for a free-radical copper (II) complex.
Received: 19 July 1996 / Accepted: 16 October 1996 相似文献
18.
Pernilla Wittung-Stafshede Michael G. Hill Ester Gomez A. J. Di Bilio B. Göran Karlsson Johan Leckner J. R. Winkler Harry B. Gray B. G. Malmström 《Journal of biological inorganic chemistry》1998,3(4):367-370
Cyclic voltammetry has been used to determine the reduction potentials of blue (Pseudomonas aeruginosa azurin) and purple (Thermus thermophilus CuA domain) copper proteins unfolded by guanidine hydrochloride. These Cu(II/I) potentials [456 (azurin); 453 (CuA) mV vs., NHE] are higher than those of the folded proteins. The downshift of the potential in the folded state can be accounted
for by assuming that rack-induced axial coordination stabilizes Cu(II) relative to Cu(I) in a protein-encapsulated active
site.
Received: 3 March 1998 / Accepted: 6 April 1998 相似文献
19.
The intramolecular electron-transfer rate constant for the Cu(II)–topaNH2⇌ Cu(I)–topaSQ equilibrium in methylamine oxidase has been measured by temperature-jump relaxation techniques. At pH 7.0 the estimated kobs = 150±30 s–1 for both methylamine and benzylamine; assuming the equilibrium constant is ≈0.7–1 at pH 7.0 and 296 K, this would correspond
to a forward electron-transfer rate constant kET≈ 60–75 s–1. Although substantially slower than the previously determined kET≈ 20 000 s–1 for pea seedling amine oxidase [5] steady-state kinetics measurements established that kET > kcat≈ 4–10 s–1. Thus the Cu(I)-semiquinone state is a viable intermediate in methylamine oxidase turnover.
Received: 16 August 1995 / Accepted: 21 December 1995 相似文献
20.
Copper amine oxidases catalyze the oxidative deamination of primary amines operating through a ping-pong bi bi mechanism, divided into reductive and oxidative half-reactions. Considerable debate still exists regarding the role of copper in the oxidative half-reaction, where O2 is reduced to H2O2. Substrate-reduced amine oxidases display an equilibrium between a Cu(II) aminoquinol and a Cu(I) semiquinone, with the magnitude of the equilibrium constant being dependent upon the enzyme source. The initial electron transfer to dioxygen has been proposed to occur from either the reduced Cu(I) center or the reduced aminoquinol cofactor. In order for Cu(I) to be involved, it must be shown that the rate of electron transfer (k
ET) between the aminoquinol and Cu(II) is sufficiently rapid to place the Cu(I) semiquinone moiety on the mechanistic pathway. To further explore this issue, we measured the intramolecular electron transfer rate for the Cu(II) aminoquinol ⇆ Cu(I) semiquinone equilibrium in Arthrobacter globiformis amine oxidase (AGAO) by temperature-jump relaxation techniques. The results presented herein establish that k
ET is greater than the rate of catalysis (k
cat) for the preferred amine substrate β-phenylethylamine at three pH values, thereby permitting the Cu(I) semiquinone to be a viable catalytic intermediate during enzymatic reoxidation in this enzyme. The data show that k
ET is approximately equivalent at pH 6.2 and 7.2, being 2.5 times k
cat for these pH values. At pH 8.2, however, k
ET decreases, becoming comparable to k
cat. Potential reasons for the decreased k
ET at basic pH are presented. The implications of these results in light of a previously published study measuring reoxidation rates of substrate-reduced AGAO are also addressed. 相似文献