The Competition Between Chemistry and Biology in Assembling Iron–Sulfur Derivatives: Molecular Structures and Electrochemistry. Part VI. {[Fe 4 S 4 ](S γ Cys ) 3 (nonthiolate ligand)} Proteins

Zanello, Piero; Corsini, Maddalena

doi:10.1016/b978-0-12-409547-2.12708-8

Cited by 4 publications

(3 citation statements)

References 250 publications

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“…Potentials of these clusters are modulated by the protein environment, with low-potential ferredoxins ranging from −150 mV to −700 mV and HiPIPs from +100 mV to +400 mV vs normal hydrogen electrode (NHE) . Importantly, [4Fe-4S]-ferredoxins can access only one of these two redox couples during their physiological operation. , The [4Fe-4S] cluster in FeP possesses unique redox properties in that (1) it can attain an all-ferrous state, [4Fe-4S] 0 , which is more reduced than canonical [4Fe-4S] clusters − and has only been reported in rare cases in biological systems , and model complexes, , and (2) it is able to reversibly access two redox couples ([4Fe-4S] 2+ /[4Fe-4S] 1+ and [4Fe-4S] 1+ /[4Fe-4S] 0 ) within the biological redox range (approximately −1 V to +1 V) (Table ). This observation naturally raises the question as to whether FeP can operate as a two-electron donor to MoFeP (see section for more on this topic).…”

Section: Structural and Physical Determinants Of Electron Transfer In...mentioning

confidence: 99%

Electron Transfer in Nitrogenase

2020

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Nitrogenase is the only enzyme capable of reducing N2 to NH3. This challenging reaction requires the coordinated transfer of multiple electrons from the reductase, Fe-protein, to the catalytic component, MoFe-protein, in an ATP-dependent fashion. In the last two decades, there have been significant advances in our understanding of how nitrogenase orchestrates electron transfer (ET) from the Fe-protein to the catalytic site of MoFe-protein and how energy from ATP hydrolysis transduces the ET processes. In this review, we summarize these advances, with focus on the structural and thermodynamic redox properties of nitrogenase component proteins and their complexes, as well as on new insights regarding the mechanism of ET reactions during catalysis and how they are coupled to ATP hydrolysis. We also discuss recently developed chemical, photochemical, and electrochemical methods for uncoupling substrate reduction from ATP hydrolysis, which may provide new avenues for studying the catalytic mechanism of nitrogenase.

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Section: Structural and Physical Determinants Of Electron Transfer In...mentioning

confidence: 99%

Electron Transfer in Nitrogenase

2020

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“…The main contribution to the SOC matrix elements should come from the orbital pairs that have different occupations in two coupled spin states. 60 These are orbital pairs (2,5), (1,5), and (1,4) for the clusters with charges 2−, 1−, and 0, respectively. Three components (x, y, and z) of the spin−orbit operator act on a molecular orbital by rotating it by 90°around x-, y-, or z-axis.…”

Section: Resultsmentioning

confidence: 99%

“…Rubredoxin is a protein that is essential for electron transfer in many biological systems. 1 It is involved in variety of enzymecatalyzed processes, such as nitrate reduction, 2 alkane oxidation, 3 methanogenesis, 4 carbon fixation, 5 and detoxification of reactive oxygen species. 6,7 Rubredoxin plays a crucial role in photosystem II activity within a broad variety of oxygenic organisms.…”

Section: Introductionmentioning

confidence: 99%

Spin-Forbidden Transitions between Electronic States in the Active Site of Rubredoxin

2016

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Rubredoxin is a small iron-sulfur protein involved in biological electron transfer, which is accomplished by changing the oxidation state of the iron atom in the active site. We investigate the possibility of spin-forbidden transitions between the lowest energy electronic states with different spin multiplicities in the rubredoxin active site models [Fe(SCH)] (n = 2-, 1-, 0) using nonadiabatic transition state theory (NA-TST). The equilibrium structures, minimum energy crossing point structures and Hessians were obtained with density functional theory. The spin-orbit coupling (SOC) was calculated with the complete active space configuration interaction method using the two-electron spin-orbit Breit-Pauli Hamiltonian. We found several crossings between the lowest energy spin states associated with the changes in Fe coordination. However, only triplet/quintet crossings in [Fe(SCH)] and [Fe(SCH)], as well as a quartet/sextet crossing in [Fe(SCH)] are characterized by nonzero first-order SOC responsible for transitions between these spin states. The rates of spin-forbidden transitions in the [Fe(SCH)] complex are 1 and 2 orders of magnitude higher than the rates in the [Fe(SCH)] and [Fe(SCH)] complexes, respectively. These rate differences are related to a large variation of the SOC between the complexes with different charges, which in turn comes from different molecular orbitals involved in the spin-flip transitions. Finally, we demonstrate that the differences between the NA-TST rates and the rates calculated under the assumption of completely spin-allowed transitions could be as large as 4 orders of magnitude. This means that even in qualitative discussions of the reaction mechanisms involving changes in spin states the partially spin-forbidden nature of the transitions between these states must be taken into account.

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Structure and electrochemistry of proteins harboring iron-sulfur clusters of different nuclearities. Part III. [4Fe-4S], [3Fe-4S] and [2Fe-2S] iron-sulfur proteins

Zanello

2018

Journal of Structural Biology

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A systematic rationalization of the hundreds of proteins harboring iron-sulfur clusters and able to exhibit the most diverse biological functions is missing. In this picture we have already reviewed structure/electrochemistry of metalloproteins expressing single types of iron-sulfur centres [namely, {Fe(Cys)}, {[FeS](Cys)}, {[FeS](Cys)(X)} (X = Asp, Arg, His), {[FeS](Cys)(His)}, {[FeS](Cys)}, {[FeS](Cys)} and {[FeS](S)(nonthiolate ligand)}] and their synthetic analogs. Recently we are focussing on structure/electrochemistry of metalloproteins containing iron-sulfur centres of different nuclearities. Having started such a subject with proteins harboring [4Fe-4S] and [2Fe-2S] (Zanello, 2017c) as well as [4Fe-4S] and [3Fe-4S] (Zanello, in press) clusters, we now provide the state of art of proteins harboring [4Fe-4S], [3Fe-4S] and [2Fe-2S] clusters, a subject that resulted strictly limited to enzymes active in the respiratory Complex II.

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The Competition Between Chemistry and Biology in Assembling Iron–Sulfur Derivatives: Molecular Structures and Electrochemistry. Part VI. {[Fe 4 S 4 ](S γ Cys ) 3 (nonthiolate ligand)} Proteins

Cited by 4 publications

References 250 publications

Electron Transfer in Nitrogenase

Electron Transfer in Nitrogenase

Spin-Forbidden Transitions between Electronic States in the Active Site of Rubredoxin

Structure and electrochemistry of proteins harboring iron-sulfur clusters of different nuclearities. Part III. [4Fe-4S], [3Fe-4S] and [2Fe-2S] iron-sulfur proteins

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