A mössbauer investigation of oxidized Fe4S4 HiPIP II from Ectothiorohodospira halophila

Bertini, Ivano; Campos, António P.; Teixeira, Miguel; Luchinat, Claudio

doi:10.1016/0162-0134(93)80043-9

Cited by 35 publications

(41 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The latter indicates a special Fe subsite with an additional coordinating ligand in a distorted geometry (24)(25)(26). The average isomer shift for this cluster in this state is δ av ¼ 0.34 mms −1 at 160 K, being in the range of those reported for HiPIP-like cubane clusters (22).…”

Section: Assignment Of the [Fes]supporting

confidence: 50%

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

View full text Add to dashboard Cite

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 ...

show abstract

Section: Assignment Of the [Fes]supporting

confidence: 50%

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

View full text Add to dashboard Cite

show abstract

“…The HiPIP II from E. halophila represents the limiting case among the proteins of its class as it occurs in just one isomeric state (a=100%) and as it performs remarkably slow electron relaxation (compare ref. 14 in Bertini et al [13]). This can be interpreted by the assumption that the excited Orbach state represents the HiPIP cluster in the minor electronic isomer.…”

Section: Discussionmentioning

confidence: 89%

“…Since the electrons are odd, there remains a total spin of S=1/2. Except for the HiPIP II from E. halophila [13,16,19], all oxidized HiPIPs show a characteristic ratio of at least two electronic isomers in room temperature NMR experiments, e.g. 80%:20% for the HiPIP I from E. halophila [21].…”

Section: Introductionmentioning

confidence: 99%

Dynamics of wild-type HiPIPs: a Cys77Ser mutant and a partially unfolded HiPIP

et al. 2002

Self Cite

View full text Add to dashboard Cite

The temperature dependence of the mean square displacement of the (57)Fe nuclei due to motion faster than 100 ns are measured by temperature-dependent Mössbauer spectroscopy for oxidized and reduced HiPIPs from Ectothiorhodospira halophila, Chromatium vinosum WT and a Cys77Ser mutant. The behaviour is interpretable in the frame of the general model of protein dynamics distinguishing two temperature intervals. The character of harmonic and quasi-diffusional modes in HiPIPs is discussed. Dynamic information obtained from Mössbauer spectroscopy and Fe K-edge EXAFS are compared. Structure dynamics of the iron-sulfur cluster in the partially unfolded reduced HiPIP from C. vinosum was investigated by Mössbauer spectroscopy and EXAFS, indicating an intact metal centre and a protein backbone with a largely collapsed secondary structure. The role of the cofactor during protein folding is discussed. Differences in the dynamics between the native protein and the molten globule are found at physiological temperatures only. The structure and dynamic behaviour of the [Fe(4)S(4)]Cys(3)Ser cluster in the Cys77Ser mutant of the HiPIP from C. vinosum are analysed. The temperature dependence of electron relaxation in oxidized HiPIPs is investigated by Mössbauer spectroscopy and analysed theoretically, considering spin-spin and spin-lattice relaxation. The latter consists of contributions from direct phonon bottleneck and Orbach mechanisms. The data agree with former pulsed EPR results. Orbach relaxation is interpreted as due to transitions between electronic isomers of oxidized HiPIPs. With this interpretation, the energetic difference between both isomers equals the energy gap estimated from the temperature dependence of the Orbach relaxation.

show abstract

“…This protein carries a Fe 4 -S 4 cubane cluster that is experimentally found to behave as a S = 1/2 paramagnet in the oxidized state: this can be interpreted in terms of where each pair is located as the net result of two opposing interactions, namely, of superexchange, via the bridging sulfides, favoring antiparallel coupling of individual ion spins [125], and of double-exchange, associated with electron delocalization over the pair, favoring parallel spin coupling [126][127][128]. In this situation, the ''ferric'' couple has spin 4 and is forced by the mixed pair, formally comprising of two Fe 2.5+ , thus having spin 9/2, in an antiparallel spin configuration.…”

Section: Paramagnetism In Solid-state Nmrmentioning

confidence: 99%

NMR of sedimented, fibrillized, silica-entrapped and microcrystalline (metallo)proteins

Ravera

Schubeis

Martelli

et al. 2015

Journal of Magnetic Resonance

Self Cite

View full text Add to dashboard Cite

A mössbauer investigation of oxidized Fe4S4 HiPIP II from Ectothiorohodospira halophila

Cited by 35 publications

References 33 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

Dynamics of wild-type HiPIPs: a Cys77Ser mutant and a partially unfolded HiPIP

NMR of sedimented, fibrillized, silica-entrapped and microcrystalline (metallo)proteins

Contact Info

Product

Resources

About