Thermodynamic influences on the fidelity of iron‐sulphur cluster formation in proteins

Armstrong, Fräser A.; Williams, R. J. P.

doi:10.1016/s0014-5793(99)00545-1

Cited by 6 publications

(3 citation statements)

References 29 publications

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“…However, at the 0 level, Fe 2+ or indeed Zn 2+ can stabilize the cluster by binding to reform a cubane. The observation that Fe(II) binds more tightly than Zn(II) shows the importance of resonance stabilization (50). The reversibility of [4Fe-4S] disassembly as far as [3Fe-4S] is, therefore, confirmed for a 10 Square-wave voltammetry produces better resolution of two or more redox processes that have quite similar reduction potentials.…”

Section: Discussionmentioning

confidence: 86%

Investigations of the Oxidative Disassembly of Fe−S Clusters in Clostridium pasteurianum 8Fe Ferredoxin Using Pulsed-Protein-Film Voltammetry

Camba

Armstrong²

2000

Biochemistry

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Rapid responses of biological [4Fe-4S] clusters to conditions of oxidative stress have been studied by protein-film voltammetry by using precise pulses of electrode potential to trigger reactions. Investigations with Clostridium pasteurianum 8Fe ferredoxin exploit the fact that [3Fe-4S] clusters display a characteristic pattern of voltammetric signals, so that their appearance and disappearance after an oxidative pulse can be tracked unambiguously under electrochemical control. Adsorbed to monolayer coverage at a graphite electrode, the protein initially shows a strong signal (B') at -0.36 V vs standard hydrogen electrode due to two [4Fe-4S](2+/+) clusters at similar potentials. Short square pulses (0.1-5 s) to potentials in the range 0.5-0.9 V cause extensive loss of B', and new signals appear (A'and C') that arise from [3Fe-4S] species (+/0 and 0/2- couples). The A' and B' intensities quantify transformations which are induced by the pulse and which occur subsequently when more reducing conditions are restored. Optimal [3Fe-4S] formation (in excess over [4Fe-4S]) is achieved with a 3-s pulse to 0.7 V, following which there is rapid partial recovery to yield a 1:1 3Fe:4Fe ratio, consistent with 7Fe protein. Thus, a 6Fe protein is formed, but one of the clusters is rapidly repaired. The [3Fe-4S]:[4Fe-4S] ratio follows a bell-shaped curve spanning the same potential range that defines complete loss of signals, while double-pulse experiments show that [3Fe-4S](+) resists further oxidative damage. Oxidative disassembly involves successive one-electron oxidations of [4Fe-4S] (i.e., 2+ --> 3+ --> 4+), with [3Fe-4S](+) being a relatively stable byproduct, that is, not an intermediate. Disassembly of [3Fe-4S] in the 7Fe protein continues after reducing conditions are restored, with lifetimes depending on oxidation level; thus 1+ (most stable) > 0 > 2-. In the presence of Fe(2+), the 0 level is stabilized by conversion back to [4Fe-4S](2+/+). By pulsing in the presence of Zn(2+), the [3Fe-4S] clusters that are formed are trapped rapidly as their Zn adducts.

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Section: Discussionmentioning

confidence: 86%

Investigations of the Oxidative Disassembly of Fe−S Clusters in Clostridium pasteurianum 8Fe Ferredoxin Using Pulsed-Protein-Film Voltammetry

Camba

Armstrong²

2000

Biochemistry

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“…Another field in which the role of the deformation of the reacting moieties may play a role is enzyme catalysis. Some authors − suggest that the protein environment around the active site of enzymes adopts a conformation that is close to the unconstrained geometry of the transition state or the products. However, this issue is still under debate for enzymes because this view has been refuted by others. , Nevertheless, this concept is still not part of standard descriptions of the factors determining the bonding energetics of organometallic complexes that are found in inorganic chemistry textbooks.…”

Section: Resultsmentioning

confidence: 99%

Bond Energies and Bonding Interactions in Fe(CO)₅_-_n(N₂)_n (n = 0−5) and Cr(CO)₆_-_n(N₂)_n (n = 0−6) Complexes: Density Functional Theory Calculations and Comparisons to Experimental Data

2001

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Metal−N2 bond energies have been calculated for the Fe(CO)5 - n (N2) n (n = 1−5) and Cr(CO)6 - n (N2) n (n = 1−6) complexes using density-functional theory (DFT). Bond enthalpies calculated using the gradient corrected BP86 functional are in good agreement with the available experimental data. An energy decomposition procedure and a population analysis were performed for all of the complexes to quantitatively characterize the interactions of N2 and CO with the relevant coordinatively unsaturated metal species. In all cases, the metal−N2 bond is weaker than the metal−CO bond because CO is both a better donor and a better acceptor of electron density. Calculated bond energies for Cr−N2 bonds for the lowest energy isomers of the chromium complexes are 24, 23, 22, 21, 20, and 25 kcal/mol for n = 1−6, respectively. The trend of decreasing bond energy with added N2 ligands is a result of weaker orbital interactions. The exception is Cr(N2)6, which is predicted to be more stable than the CO containing complexes. This increase in stability is ascribed to the absence of a CO trans effect. In contrast, the Fe−N2 bond energies for the lowest energy isomers in the series are 24, 17, 14, 10, and 5 kcal/mol for n = 1−5, respectively. Although iron has a larger orbital interaction with dinitrogen ligands than chromium, the 16-electron iron complexes have to deform substantially when going from their ground triplet states to their final pentacoordinated singlet geometries. An energy cost that increases as the number of N2 ligands increases is associated with this deformation. For chromium complexes, this deformation term does not significantly decrease the bond energy, but the magnitude of this term becomes the dominant factor in the differences in bond energies in the dinitrogenated iron complexes.

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“…Overall, protein-bound cuboidal clusters bind a variety of monovalent and divalent ions to afford products to which a cubane-type structure is assigned. , While no MFe 3 S 4 cluster of biosynthetic origin has yet been found, it would be not entirely surprising if such clusters do appear naturally, given their ease of formation and usually stable structures. This matter has been considered by others …”

Section: Structural Conversionsmentioning

confidence: 95%

Synthetic Analogues of the Active Sites of Iron−Sulfur Proteins

2003

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Contents 1. Introduction 527 2. Rubredoxin Site Analogues 530 2.1. Preparation 530 2.2. Structures 530 2.3. Properties 531 3. Analogues of Binuclear (Fe 2 S 2 ) Sites 532 3.1. Preparation 532 3.2. Structures 533 3.3. Properties 533 3.4. Heteroligated Clusters 534 4. Analogues of Trinuclear (Fe 3 S 4 ) Sites 535 4.1. Linear Clusters 535 4.2. Cuboidal Clusters 536 4.3. Reactivity 537 5. Analogues of Tetranuclear (Fe 4 S 4 ) Sites 538 5.1. Electron-Transfer Series 538 5.2. [Fe 4 S 4 ] 3+ Clusters 540 5.3. [Fe 4 S 4 ] 2+ Clusters 542 5.4. [Fe 4 S 4 ] + Clusters 543 5.5. [Fe 4 S 4 ] 0 Clusters 543 5.6. Principal Structural Features 544 5.7. Specialized Clusters 545 5.7.1. Peptide Clusters 545 5.7.2. Site-Differentiated Clusters 546 5.7.3. Bridged Assemblies 549 6. Mo ¨ssbauer Parameters and Oxidation States 551 7. Structural Conversions 552 8. Perspective 554 9. Acknowledgement 555 10. Abbreviations 555 11. References 555Richard H. Holm was born in Boston, MA, spent his younger years on Nantucket Island and Cape Cod, and graduated from the University of Massachusetts (B.S.) and Massachusetts Institute of Technology (Ph.D.) He has served on the faculties of the University of Wisconsin, Massachusetts Institute of Technology, and Stanford University. Since 1980, he has been at Harvard University, where he has been Chair of the Department of Chemistry and, from 1983, Higgins Professor of Chemistry. His research interests are centered in inorganic and bioinorganic chemistry, with particular reference to the synthesis and properties of molecules whose structures and reactions are pertinent to biological processes. Venkateswara Rao Pallem was born in Hyderabad, India. He received his M.Sc. degree in chemistry in 1995 from Osmania University, Hyderabad, and his Ph.D. in chemistry in 2001 at the Indian Institute of Technology, Bombay, India, under the guidance of Professor Chebrolu P. Rao. He is currently working as a postdoctoral fellow with Professor Richard H. Holm. His research interests include the design and study of synthetic analogues of biologically related molecules.

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Thermodynamic influences on the fidelity of iron‐sulphur cluster formation in proteins

Cited by 6 publications

References 29 publications

Investigations of the Oxidative Disassembly of Fe−S Clusters in Clostridium pasteurianum 8Fe Ferredoxin Using Pulsed-Protein-Film Voltammetry

Investigations of the Oxidative Disassembly of Fe−S Clusters in Clostridium pasteurianum 8Fe Ferredoxin Using Pulsed-Protein-Film Voltammetry

Bond Energies and Bonding Interactions in Fe(CO)₅_-_n(N₂)_n (n = 0−5) and Cr(CO)₆_-_n(N₂)_n (n = 0−6) Complexes: Density Functional Theory Calculations and Comparisons to Experimental Data

Synthetic Analogues of the Active Sites of Iron−Sulfur Proteins

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Thermodynamic influences on the fidelity of iron‐sulphur cluster formation in proteins

Cited by 6 publications

References 29 publications

Investigations of the Oxidative Disassembly of Fe−S Clusters in Clostridium pasteurianum 8Fe Ferredoxin Using Pulsed-Protein-Film Voltammetry

Investigations of the Oxidative Disassembly of Fe−S Clusters in Clostridium pasteurianum 8Fe Ferredoxin Using Pulsed-Protein-Film Voltammetry

Bond Energies and Bonding Interactions in Fe(CO)5-n(N2)n (n = 0−5) and Cr(CO)6-n(N2)n (n = 0−6) Complexes: Density Functional Theory Calculations and Comparisons to Experimental Data

Synthetic Analogues of the Active Sites of Iron−Sulfur Proteins

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Product

Resources

About

Bond Energies and Bonding Interactions in Fe(CO)₅_-_n(N₂)_n (n = 0−5) and Cr(CO)₆_-_n(N₂)_n (n = 0−6) Complexes: Density Functional Theory Calculations and Comparisons to Experimental Data