The metal site of stellacyanin: EXAFS studies of the Cu(II), Cu(I), Ni(II) and Co(II) derivatives

Feiters, Martinus C.; Dahlin, Stefan; Reinhammar, Bengt

doi:10.1016/0167-4838(88)90200-2

Cited by 17 publications

(17 citation statements)

References 32 publications

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“…4 d–i). This suggested that stellacyanin could control the concentration of aryloxy radicals, which was consistent with the hypothesis in the literature 32 , 33 . In addition, in the ESR spectra of the urushiol/H 2 O emulsion with laccase, when the drying time was 5 min, there were two signals at g = 2.0203 and 1.9874.…”

Section: Resultssupporting

confidence: 92%

“…Obviously, stellacyanin inhibited certain radical polymerization, which involved the reactions both on the alkyl chain of urushiol and on the phenyl ring of urushiol. Since stellacyanin possessed a low oxidation–reduction potential of 184 mV and could act as a quinone/semiquinone reductase, its role was assumed to regulate the concentrations of aryloxy radicals and quinones involved in the laccase-catalysed oxidation of urushiol 31 – 33 . Thus, the effect of stellacyanin on laccase-catalyzed polymerization of urushiol could be due to its inhibition of free radical concentration.…”

Section: Resultsmentioning

confidence: 99%

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Polymerization mechanism of natural lacquer sap with special phase structure

Yang

Chen

Zhu

et al. 2020

Sci Rep

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Lacquer sap is a water-in-oil natural emulsion with high viscosity. in nature, it exudes from the phloem of lacquer tree to repair its wounds in the presence of o 2. So far, it is unclear how rapid and smooth polymerization of urushiol is achieved in such a viscous sap. Here, we find that there is a diffuse interface layer with 2.43 nm of thickness between two phases. The interface layer consists of urushiol, urushiol-laccase complex, urushiol-stellacyanin complex and water-insoluble glycoprotein. Polymerization of urushiol is realized by multicomponent synergistic effect. Radicals are first formed by laccase-catalyzed oxidation of urushiol at the interface layer, then are transferred to the urushiol oil phase via wate-insoluble glycoprotein and initiate the polymerization of urushiol there. Stellacyanin inhibits the formation of certain radicals and controls the concentration of phenoxy radicals at the interface layer. Through the inhibition of radicals by stellacyanin and the electron transfer mediated by water-insoluble glycoprotein, the polymerization of urushiol at the interface layer is inhibited. This ensures that o 2 can continuously penetrate into the aqueous phase to oxidize the reduced laccase so that the urushiol polymerization can continue smoothly. this polymerization mechanism provides an idea for developing new chemical reaction systems.

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Polymerization mechanism of natural lacquer sap with special phase structure

Yang

Chen

Zhu

et al. 2020

Sci Rep

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“…Groeneveld et al [3] in their study of the pH-dependence of the EXAFS of the same protein reached a similar conclusion concerning the long Cu-S distances. A similar conclusion was reached by Feiters et aL for stellacyanin [45]. Again, for umecyanln Sykes and cowork~ [46] report that no fourth Cu-ligand (possibly ~ ~ouor) is discernable in the EXAFS of the Cu-site.…”

Section: Copper Coordinationsupporting

confidence: 71%

EXAFS analysis of the pH dependence of the blue-copper site in amicyanin from Thiobacillus versutus

Lommen

Pandya

Koningsberger

et al. 1991

Biochimica et Biophysica Acta (BBA) - Protein Structure and Mol

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The room temperature Cu K-edge EXAFS (extended X-ray absorption fine structure) spectrum of reduced and oxidized amicyanin, the blue copper protein from Thiobacillus versutus, was measured at low and high pH. The data interpretation was partly based on independent NMR evidence for the occurrence of a ligand histidine protonation at low pH (pKa = 6.9) in the reduced protein. In the oxidized protein two nitrogen-donors (from two histidines; Cu-N distances 1.95-2.01 A and 1.86-1.89 A) and a sulfur-donor (from a cysteine; Cu-S distance 2.11-2.13 A) were identified and the coordination appears independent of pH. Upon reduction at high pH the Cu-S bond and one of the Cu-N bonds lengthen slightly (from 2.11 to 2.19 A and from 2.01 to 2.18 A, respectively). Upon lowering of the pH one of the N-donors of the Cu in reduced amicyanin disappears from the Cu EXAFS and a second S-donor (from a methionine) becomes visible at 2.41 A from the Cu. The Debye-Waller factors are compatible with a Cu-N vibrational stretch frequency in the range of 150-250 cm-1 and one greater than 285 cm-1, and a Cu-S vibrational stretch frequency of about 150 cm-1 (Cu-Smet; reduced amicyanin at low pH) and one in the range of 230-800 cm-1 (Cu-Scys).

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“…Rather, the relative constancy of RR frequencies can be taken as an indication of a conserved short Cu-S(Cys) bond of ~2.13 in all blue copper sites. On the basis of its Raman frequencies (Figure 4), stellacyanin is also likely to have a short Cu-S(Cys) bond, despite the suggestion of a longer 2.2 Á Cu-S(Cys) distance from EXAFS analyses (Peisach et al, 1982;Feiters et al, 1988).…”

Section: Resultsmentioning

confidence: 99%

“…Rather, the relative constancy of RR frequencies can be taken as an indication of a conserved short Cu-S(Cys) bond of -2.13 %, in all blue copper sites. On the basis of its Raman frequencies (Figure 4), stellacyanin is also likely to have a short Cu-S(Cys) bond, despite the suggestion of a longer 2.2 A Cu-S(Cys) distance from EXAFS analyses (Peisach et al, 1982;Feiters et al, 1988). Whereas vibrational frequencies in resonance Raman spectra are solely a function of the structure of the molecule in the electronic ground state, vibrational intensities are related to the change in the geometry of the chromophore in the electronic excited state (Carey, 1982).…”

Section: Deuterium Isotope Shijts In Rr Spectramentioning

confidence: 99%

Resonance Raman spectra of plastocyanin and pseudoazurin: evidence for conserved cysteine ligand conformations in cupredoxins (blue copper proteins)

Han

Adman²,

Beppu³

et al. 1991

Biochemistry

108

139

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New resonance Raman (RR) spectra at 15 K are reported for poplar (Populus nigra) and oleander (Oleander nerium) plastocyanins and for Alcaligenes faecalis pseudoazurin. The spectra are compared with those of other blue copper proteins (cupredoxins). In all cases, nine or more vibrational modes between 330 and 460 cm-1 can be assigned to a coupling of the Cu-S(Cys) stretch with Cys ligand deformations. The fact that these vibrations occur at a relatively constant set of frequencies is testimony to the highly conserved ground-state structure of the Cu-Cys moiety. Shifts of the vibrational modes by 1-3 cm-1 upon deuterium exchange can be correlated with N-H...S hydrogen bonds from the protein backbone to the sulfur of the Cys ligand. There is marked variability in the intensities of these Cys-related vibrations, such that each class of cupredoxin has its own pattern of RR intensities. For example, plastocyanins from poplar, oleander, French bean, and spinach have their most intense feature at approximately 425 cm-1; azurins show greatest intensity at approximately 410 cm-1, stellacyanin and ascorbate oxidase at approximately 385 cm-1, and nitrite reductase at approximately 360 cm-1. These variable intensity patterns are related to differences in the electronic excited-state structures. We propose that they have a basis in the protein environment of the copper-cysteinate chromophore. A further insight into the vibrational spectra is provided by the structures of the six cupredoxins for which crystallographic refinements at high resolution are available (plastocyanins from P. nigra, O. nerium, and Enteromorpha prolifera, pseudoazurin from A. faecalis, azurin from Alcaligenes denitrificans, and cucumber basic blue protein). The average of the Cu-S(Cys) bond lengths is 2.12 +/- 0.05 A. Since the observed range of bond lengths falls within the precision of the determinations, this variation is considered insignificant. The Cys ligand dihedral angles are also highly conserved. Cu-S gamma-C beta-C alpha is always near -170 degrees and S gamma-C beta-C alpha-N near 170 degrees. As a result, the Cu-S gamma bond is coplanar with the Cys side-chain atoms and part of the polypeptide backbone. The coplanarity accounts for the extensive coupling of Cu-S stretching and Cys deformation modes as seen in the RR spectrum. The conservation of this copper-cysteinate conformation in cupredoxins may indicate a favored pathway for electron transfer.

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The metal site of stellacyanin: EXAFS studies of the Cu(II), Cu(I), Ni(II) and Co(II) derivatives

Cited by 17 publications

References 32 publications

Polymerization mechanism of natural lacquer sap with special phase structure

Polymerization mechanism of natural lacquer sap with special phase structure

EXAFS analysis of the pH dependence of the blue-copper site in amicyanin from Thiobacillus versutus

Resonance Raman spectra of plastocyanin and pseudoazurin: evidence for conserved cysteine ligand conformations in cupredoxins (blue copper proteins)

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