A Refined Model for [Fe3S4]0 Clusters in Proteins

Bentrop, Detlef; Bertini, Ivano; Borsari, Marco; Cosenza, Grazia; Luchinat, Claudio; Niikura, Yohei

doi:10.1002/1521-3773(20001016)39:20<3620::aid-anie3620>3.0.co;2-t

Cited by 25 publications

(8 citation statements)

References 26 publications

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“…18,21 This is supported by results from spectroscopy, crystallography and site-directed mutagenesis, and it is likely that protonation occurs on one of the µ-sulfido groups. [21][22][23][24] High-resolution structures (1.4 Å) have been obtained for both oxidised ([3Fe-4S] ϩ ) and reduced ([3Fe-4S] 0 ) forms of A.v. FdI at high and low pH.…”

Section: Gated Electron Transfer At Protein Active Sitesmentioning

confidence: 99%

Insights from protein film voltammetry into mechanisms of complex biological electron-transfer reactionsBased on the presentation given at Dalton Discussion No. 4, 10–13th January 2002, Kloster Banz, Germany.

Armstrong

2002

J. Chem. Soc., Dalton Trans.

117

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Section: Gated Electron Transfer At Protein Active Sitesmentioning

confidence: 99%

Insights from protein film voltammetry into mechanisms of complex biological electron-transfer reactionsBased on the presentation given at Dalton Discussion No. 4, 10–13th January 2002, Kloster Banz, Germany.

Armstrong

2002

J. Chem. Soc., Dalton Trans.

117

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“…The [3Fe-4S] cluster rapidly binds a proton in the one-electron-reduced (0) level, despite the fact that it is buried approximately 8 Å below the protein surface. The exact site of proton binding has not been established, but it is most likely to be one of the cluster μ 2 -sulfido ligands ( , ). Other [3Fe-4S]-containing proteins exhibit similar behavior, and there is no evidence for proton binding to the oxidized cluster ( , ).…”

mentioning

confidence: 99%

Mechanisms of Redox-Coupled Proton Transfer in Proteins: Role of the Proximal Proline in Reactions of the [3Fe-4S] Cluster in Azotobacter vinelandii Ferredoxin I^,

et al. 2003

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The 7Fe ferredoxin from Azotobacter vinelandii (AvFdI) contains a [3Fe-4S](+/0) cluster that binds a single proton in its reduced level. Although the cluster is buried, and therefore inaccessible to solvent, proton transfer from solvent to the cluster is fast. The kinetics and energetics of the coupled electron-proton transfer reaction at the cluster have been analyzed in detail by protein-film voltammetry, to reveal that proton transfer is mediated by the mobile carboxylate of an adjacent surface residue, aspartate-15, the pK of which is sensitive to the charge on the cluster. This paper examines the role of a nearby proline residue, proline-50, in proton transfer and its coupling to electron transfer. In the P50A and P50G mutants, a water molecule has entered the cluster binding region; it is hydrogen bonded to the backbone amide of residue-50 and to the Asp-15 carboxylate, and it is approximately 4 A from the closest sulfur atom of the cluster. Despite the water molecule linking the cluster more directly to the solvent, proton transfer is not accelerated. A detailed analysis reveals that Asp-15 remains a central part of the mechanism. However, the electrostatic coupling between cluster and carboxylate is almost completely quenched, so that cluster reduction no longer induces such a favorable shift in the carboxylate pK, and protonation of the base no longer induces a significant shift in the pK of the cluster. The electrostatic coupling is crucial for maintaining the efficiency of proton transfer both to and from the cluster, over a range of pH values.

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“…The subject was a buried [3Fe−4S] cluster in a small ferredoxin (FdI) from Azotobacter vinelandii, unusual in that the reduced ([3Fe−4S] 0 ) form binds a proton at neutral pH (the p K is around 8). The proton probably binds to a μ 2 -S atom and might distribute itself among all three sites . The structure of the protein has been solved to high resolution with the [3Fe−4S] cluster in different oxidation states and at high and low pH.…”

Section: Voltammetric Signals Provide Kinetic Informationmentioning

confidence: 99%

Investigating Metalloenzyme Reactions Using Electrochemical Sweeps and Steps: Fine Control and Measurements with Reactants Ranging from Ions to Gases

Vincent

Armstrong

2005

Inorg. Chem.

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Protein film voltammetry is a powerful method for probing the chemistry of redox-active sites in metalloproteins. The technique affords precise potential control over a tiny quantity of material that is manipulated on an electrode surface, providing information on ligand- or metal-exchange reactions coupled to electron transfer. This is illustrated by examples of transformations of the iron-sulfur clusters in ferredoxins. Protein film voltammetry is particularly advantageous in studies of metalloenzymes for which the current response is proportional to catalytic activity: kinetic data of extremely high signal/noise ratio are obtained for highly active enzymes. We present a series of interesting examples in which catalytic activity varies in unusual ways with applied potential, surveying information that can be obtained from cyclic voltammetry and then looking beyond this method to controlled potential-step experiments that yield kinetic and mechanistic details. Recent results on the voltammetry of the highly active [NiFe]-hydrogenase from Allochromatium vinosum illustrate how it is possible to use the precise kinetic information from potential-step experiments to diagnose subtle details of transformations between catalytically active and inactive states of an enzyme. Protein film voltammetry thus complements spectroscopic techniques and other physical methods, revealing the chemistry of systems that might appear intractable or convoluted by other means.

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A Refined Model for [Fe3S4]0 Clusters in Proteins

Cited by 25 publications

References 26 publications

Insights from protein film voltammetry into mechanisms of complex biological electron-transfer reactionsBased on the presentation given at Dalton Discussion No. 4, 10–13th January 2002, Kloster Banz, Germany.

Insights from protein film voltammetry into mechanisms of complex biological electron-transfer reactionsBased on the presentation given at Dalton Discussion No. 4, 10–13th January 2002, Kloster Banz, Germany.

Mechanisms of Redox-Coupled Proton Transfer in Proteins: Role of the Proximal Proline in Reactions of the [3Fe-4S] Cluster in Azotobacter vinelandii Ferredoxin I^,

Investigating Metalloenzyme Reactions Using Electrochemical Sweeps and Steps: Fine Control and Measurements with Reactants Ranging from Ions to Gases

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A Refined Model for [Fe3S4]0 Clusters in Proteins

Cited by 25 publications

References 26 publications

Insights from protein film voltammetry into mechanisms of complex biological electron-transfer reactionsBased on the presentation given at Dalton Discussion No. 4, 10–13th January 2002, Kloster Banz, Germany.

Insights from protein film voltammetry into mechanisms of complex biological electron-transfer reactionsBased on the presentation given at Dalton Discussion No. 4, 10–13th January 2002, Kloster Banz, Germany.

Mechanisms of Redox-Coupled Proton Transfer in Proteins: Role of the Proximal Proline in Reactions of the [3Fe-4S] Cluster in Azotobacter vinelandii Ferredoxin I,

Investigating Metalloenzyme Reactions Using Electrochemical Sweeps and Steps: Fine Control and Measurements with Reactants Ranging from Ions to Gases

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Mechanisms of Redox-Coupled Proton Transfer in Proteins: Role of the Proximal Proline in Reactions of the [3Fe-4S] Cluster in Azotobacter vinelandii Ferredoxin I^,