H2 Conversion in the Presence of O2 as Performed by the Membrane‐Bound [NiFe]‐Hydrogenase of Ralstonia eutropha

Lenz, Oliver; Ludwig, Marcus; Schubert, Torsten; Bürstel, Ingmar; Ganskow, Stefanie; Goris, Tobias; Schwarze, Alexander; Friedrich, Bärbel

doi:10.1002/cphc.200901002

Cited by 103 publications

(102 citation statements)

References 135 publications

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“…S11). Because stability of five or six coordinated clusters relates to the presence of terminal thiol ligands (24,26), there may also be an active role for the second additional cysteine, as demonstrated in recent mutation experiments (13). The presence of the second additional cysteine is thus likely to be important for the stability of the induced HiPIP-like core.…”

Section: Discussionmentioning

confidence: 92%

“…1), which show similar spectroscopic features (11,12). The presence of these residues has been shown to contribute to the oxygen stability of the R. eutropha enzyme and is therefore associated with a possible redox chemistry protecting the enzyme against oxidative stress (13). In the present work the type and redox properties of the constituent iron-sulfur clusters are investigated with the aim to (i) portray the energy coupled processes between Hase I and its redox partners and (ii) outline a relation between O 2 -tolerance and electronic/ chemical events occurring at the iron-sulfur clusters.…”

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confidence: 87%

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Characterization of a unique [FeS] cluster in the electron transfer chain of the oxygen tolerant [NiFe] hydrogenase from Aquifex aeolicus

Pandelia

Nitschke

Infossi

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

153

198

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Iron-sulfur clusters are versatile electron transfer cofactors, ubiquitous in metalloenzymes such as hydrogenases. In the oxygentolerant Hydrogenase I from Aquifex aeolicus such electron "wires" form a relay to a diheme cytb, an integral part of a respiration pathway for the reduction of O 2 to water. Amino acid sequence comparison with oxygen-sensitive hydrogenases showed conserved binding motifs for three iron-sulfur clusters, the nature and properties of which were unknown so far. Electron paramagnetic resonance spectra exhibited complex signals that disclose interesting features and spin-coupling patterns; by redox titrations three iron-sulfur clusters were identified in their usual redox states, a ½3Fe4S and two ½4Fe4S , but also a unique high-potential (HP) state was found. On the basis of 57 Fe Mössbauer spectroscopy we attribute this HP form to a superoxidized state of the [4Fe4S] center proximal to the [NiFe] site. The unique environment of this cluster, characterized by a surplus cysteine coordination, is able to tune the redox potentials and make it compliant with the ½4Fe4S 3þ state. It is actually the first example of a biological [4Fe4S] center that physiologically switches between 3þ, 2þ, and 1þ oxidation states within a very small potential range. We suggest that the (1 þ ∕2þ) redox couple serves the classical electron transfer reaction, whereas the superoxidation step is associated with a redox switch against oxidative stress.electrochemistry | EPR | iron-sulfur centers | O2-sensitivity H ydrogenases are metalloproteins occurring in the metabolic pathway of a wide variety of microbial organisms and catalyze the reversible oxidation of dihydrogen: H 2 ⇌ 2H þ þ 2e − (1). The growing interest in alternative sources of energy has focused scientific research on understanding and engineering these enzymes for future applications (2). One of the major limitations of hydrogenases, however, is their sensitivity towards oxygen. Recently, the discovery of hydrogenases that retain catalytic activity in oxygenic environments has potentially opened new applications as "green" vanguard catalysts, in particular as electrocatalysts on electrodes for biofuel cells (3,4).Aquifex aeolicus is a hyperthermophilic Knallgas bacterium with optimum growth temperature of 85°C (5). This microorganism harbors three distinct [NiFe] hydrogenases, among which Hase I is located in the aerobic respiration pathway and attached to the membrane via a diheme cytb (6). Hase I consists of two subunits; the large subunit contains the hetero-bimetallic nickel-iron site and the small subunit the electron transfer cofactors, namely iron-sulfur clusters (6). Based on spectroelectrochemical studies, this enzyme exhibits enhanced thermostability and tolerance for inhibitors (e.g., O 2 and CO) (4, 7).Although the structures of O 2 -sensitive hydrogenases are well characterized (8, 9), such information is still lacking for O 2 -tolerant enzymes. The molecular mechanism and structural determinants for this increased oxygen tolerance remain to ...

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Section: Discussionmentioning

confidence: 92%

mentioning

confidence: 87%

Characterization of a unique [FeS] cluster in the electron transfer chain of the oxygen tolerant [NiFe] hydrogenase from Aquifex aeolicus

Pandelia

Nitschke

Infossi

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

153

198

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“…A further common feature of [NiFe] H 2 ases is the ligation of the Fe by two cyanides (CN -) and one CO as observed by FTIR spectroscopy (36,(42)(43). Apart from these similarities, biochemical, electrochemical, and spectroscopic results (26,36,(43)(44)(45) suggest that O 2 tolerance of the MBH is related to the structural arrangement of its metal cofactors, rather than to the restricted access of O 2 and CO to the [NiFe] site due to a narrow gas-channel as proposed for H 2 -sensing H 2 ases (12,26,46). Notably, compared to standard H 2 ases, biosynthesis of active MBH requires a significantly larger set of maturation proteins (47)(48)(49).…”

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confidence: 88%

“…Spectroscopic studies on the MBH using EPR and FTIR techniques uncovered several features differing from those of standard enzymes (43)(44)(45)(46). The so-called Ni-A state, corresponding to oxidized, inactive unready enzyme, was not detectable in wild-type MBH.…”

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[NiFe] and [FeS] Cofactors in the Membrane-Bound Hydrogenase of Ralstonia eutropha Investigated by X-ray Absorption Spectroscopy: Insights into O₂-Tolerant H₂ Cleavage

et al. 2011

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Molecular features that allow certain [NiFe] hydrogenases to catalyze the conversion of molecular hydrogen (H2) in the presence of dioxygen (O2) were investigated. Using X-ray absorption spectroscopy (XAS), we compared the [NiFe] active site and FeS clusters in the O2-tolerant membrane-bound hydrogenase (MBH) of Ralstonia eutropha and the O2-sensitive periplasmic hydrogenase (PH) of Desulfovibrio gigas. Fe-XAS indicated an unusual complement of iron–sulfur centers in the MBH, likely based on a specific structure of the FeS cluster proximal to the active site. This cluster is a [4Fe4S] cubane in PH. For MBH, it comprises less than ~2.7 Å Fe–Fe distances and additional longer vectors of ≥3.4 Å, consistent with an Fe trimer with a more isolated Fe ion. Ni-XAS indicated a similar architecture of the [NiFe] site in MBH and PH, featuring Ni coordination by four thiolates of conserved cysteines, i.e., in the fully reduced state (Ni-SR). For oxidized states, short Ni−μO bonds due to Ni–Fe bridging oxygen species were detected in the Ni-B state of the MBH and in the Ni-A state of the PH. Furthermore, a bridging sulfenate (CysSO) is suggested for an inactive state (Niia-S) of the MBH. We propose that the O2 tolerance of the MBH is mainly based on a dedicated electron donation from a modified proximal FeS cluster to the active site, which may favor formation of the rapidly reactivated Ni-B state instead of the slowly reactivated Ni-A state. Thereby, the catalytic activity of the MBH is facilitated in the presence of both H2 and O2.

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Apparatus and Mechanism of Photosynthetic Water Splitting as Nature's Blueprint for Efficient Solar Energy Exploitation

Ренгер¹

2013

Natural and Artificial Photosynthesis

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H₂ Conversion in the Presence of O₂ as Performed by the Membrane‐Bound [NiFe]‐Hydrogenase of Ralstonia eutropha

Cited by 103 publications

References 135 publications

Characterization of a unique [FeS] cluster in the electron transfer chain of the oxygen tolerant [NiFe] hydrogenase from Aquifex aeolicus

Characterization of a unique [FeS] cluster in the electron transfer chain of the oxygen tolerant [NiFe] hydrogenase from Aquifex aeolicus

[NiFe] and [FeS] Cofactors in the Membrane-Bound Hydrogenase of Ralstonia eutropha Investigated by X-ray Absorption Spectroscopy: Insights into O₂-Tolerant H₂ Cleavage

Apparatus and Mechanism of Photosynthetic Water Splitting as Nature's Blueprint for Efficient Solar Energy Exploitation

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H2 Conversion in the Presence of O2 as Performed by the Membrane‐Bound [NiFe]‐Hydrogenase of Ralstonia eutropha

Cited by 103 publications

References 135 publications

Characterization of a unique [FeS] cluster in the electron transfer chain of the oxygen tolerant [NiFe] hydrogenase from Aquifex aeolicus

Characterization of a unique [FeS] cluster in the electron transfer chain of the oxygen tolerant [NiFe] hydrogenase from Aquifex aeolicus

[NiFe] and [FeS] Cofactors in the Membrane-Bound Hydrogenase of Ralstonia eutropha Investigated by X-ray Absorption Spectroscopy: Insights into O2-Tolerant H2 Cleavage

Apparatus and Mechanism of Photosynthetic Water Splitting as Nature's Blueprint for Efficient Solar Energy Exploitation

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H₂ Conversion in the Presence of O₂ as Performed by the Membrane‐Bound [NiFe]‐Hydrogenase of Ralstonia eutropha

[NiFe] and [FeS] Cofactors in the Membrane-Bound Hydrogenase of Ralstonia eutropha Investigated by X-ray Absorption Spectroscopy: Insights into O₂-Tolerant H₂ Cleavage