Electron‐Transfer Properties and Active‐Site Structure of the Type 1 (Blue) Copper Protein Umecyanin

Dennison, Christopher; Driessche, Gonzalez Van; Beeumen, J. Van; McFarlane, William; Sykes, A. G.

doi:10.1002/chem.19960020118

Cited by 20 publications

(16 citation statements)

References 66 publications

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“…The experimental spectrum of stellacyanin and umecyanin change at high pH: the most intense line is blue-shifted from 610 to 580 nm. 4,29,31 This shift is accompanied by changes in the EPR spectrum. 7 It has been suggested 7,12 that this is due to a change of the coordinating atom of the glutamine ligand.…”

Section: Does the Coordinating Atom Of Glutamine Change At High Ph?mentioning

confidence: 98%

“…This protein has the same set of four ligands as plastocyanin, yet its spectrum is more akin to the stellacyanin spectrum, with two instead of one strong bands, and its sequence show a high homology (46%) with stellacyanin. 29 A comparison of the calculated spectra of the different models, with and without the fourth ligand (SH 2 for plastocyanin and cucumber basic protein, OCH(NH 2 ) for stellacyanin) is presented in Table 5. Looking first at the excitation energies, we notice that the energies of the charge-transfer transitions hardly change when the axial ligand is removed (less than 360 cm -1 ).…”

Section: Effect Of the Axial Ligand In Blue Copper Proteinsmentioning

confidence: 99%

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Theoretical Study of the Structural and Spectroscopic Properties of Stellacyanin

Kerpel¹,

Pierloot²,

Ryde³

et al. 1998

J. Phys. Chem. B

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The electronic spectrum of the azurin Met121Gln mutant, a model of the blue copper protein stellacyanin, has been studied by ab initio multiconfigurational second-order perturbation theory (the CASPT2 method), including the effect of the protein and solvent by point charges. The six lowest electronic transitions have been calculated and assigned with an error of less than 2400 cm -1 . The ground-state singly occupied orbital is found to be a predominantly π antibonding orbital involving Cu3d and S cys 3p π . However, it also contains a significant amount (18%) of Cu-S cys σ antibonding character. This σ interaction is responsible for the appearance in the absorption spectrum of a band at 460 nm, with a significantly higher intensity than observed for other, axial, type 1 copper proteins (i.e., plastocyanin or azurin). The π-σ mixing is caused by the axial glutamine ligand binding at a much shorter distance to copper than the corresponding methionine ligand in the normal blue copper proteins. This explains why, based on its spectral properties, stellacyanin is classified among the rhombic type 1 copper proteins, although its structure is clearly trigonal, as it is for the axial proteins. Calculations have also been performed on structures where the glutamine model coordinates to the copper ion via the deprotonated N atom instead of the O atom. However, the resulting transition energies do not resemble the experimental spectrum obtained at normal or elevated pH. Thus, the results do not confirm the suggestion that the coordinating atom of glutamine changes at high pH.

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Section: Does the Coordinating Atom Of Glutamine Change At High Ph?mentioning

confidence: 98%

Section: Effect Of the Axial Ligand In Blue Copper Proteinsmentioning

confidence: 99%

Theoretical Study of the Structural and Spectroscopic Properties of Stellacyanin

Kerpel¹,

Pierloot²,

Ryde³

et al. 1998

J. Phys. Chem. B

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“…[188][189][190][191][192][193][194][195][196][197][198] As noted above, the largest self-exchange rate constants for these copper proteins are in the range of 10 5 -10 6 M -1 s -1 . This is equivalent to the largest values determined for inorganic copper complexes in Table 12 and is also in the same range as the rate constants calculated for the electron-transfer process between stable Cu II L and Cu I L complexes with their corresponding metastable intermediate species after correction for the conformational changes (Table 8).…”

Section: Comparative Copper(ii/i) Blue Copper Protein Propertiesmentioning

confidence: 99%

Electron Transfer by Copper Centers

2004

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“…31 Tentative proposals have been made that the alkaline transition observed in the phytocyanins may be due to the protonation/deprotonation of a surface lysine residue situated close to the protein's active site. 22,35,36 This includes a recent theoretical study of the phytocyanin called stellacyanin from which it was suggested that the change in the electrostatic field around the copper caused by the deprotonation of a surface amino acid residue could be the cause of the alkaline transition in this protein. 36 Recently, it has been suggested that deprotonation of a surface amino acid triggers a change in the protein's secondary structure, which results in the observed effect at the active site.…”

Section: Introductionmentioning

confidence: 99%

Alkaline Transition of Pseudoazurin from Achromobacter cycloclastes Studied by Paramagnetic NMR and Its Effect on Electron Transfer

Dennison

Kohzuma

1999

Inorg. Chem.

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Paramagnetic NMR studies on the Cu(II) form of pseudoazurin have been used to demonstrate that the alkaline transition of this protein results in an active site in which the axial Cu-S(Met) interaction is considerably decreased. This observation confirms the conclusion made from various other spectroscopic methods. Furthermore, we show that the alkaline transition of pseudoazurin coincides with a dramatic increase in the electron self-exchange rate constant of the protein. The self-exchange rate constant (25 °C) at pH 8.2 is 3.5 × 10 3 M -1 s -1 (I ) 0.10 M), consistent with a previously determined value (25 °C) of 2.9 × 10 3 M -1 s -1 (I ) 0.10 M) at pH 7.5. Upon increasing the pH value to 10.9 the self-exchange rate constant (25 °C) increases to 1.7 × 10 4 M -1 s -1 (I ) 0.10 M). The increased self-exchange reactivity at high pH is due to the deprotonation of a number of lysine residues that surround the hydrophobic patch of the protein, the most likely docking surface for the self-exchange process. The concomitant active site changes indicate that the deprotonation of one or more surface lysine residues is responsible for the alkaline transition in pseudoazurin.

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Electron‐Transfer Properties and Active‐Site Structure of the Type 1 (Blue) Copper Protein Umecyanin

Cited by 20 publications

References 66 publications

Theoretical Study of the Structural and Spectroscopic Properties of Stellacyanin

Theoretical Study of the Structural and Spectroscopic Properties of Stellacyanin

Electron Transfer by Copper Centers

Alkaline Transition of Pseudoazurin from Achromobacter cycloclastes Studied by Paramagnetic NMR and Its Effect on Electron Transfer

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