Reversible [4Fe-3S] cluster morphing in an O2-tolerant [NiFe] hydrogenase

Abstract

Hydrogenases catalyze the reversible oxidation of H(2) into protons and electrons and are usually readily inactivated by O(2). However, a subgroup of the [NiFe] hydrogenases, including the membrane-bound [NiFe] hydrogenase from Ralstonia eutropha, has evolved remarkable tolerance toward O(2) that enables their host organisms to utilize H(2) as an energy source at high O(2). This feature is crucially based on a unique six cysteine-coordinated [4Fe-3S] cluster located close to the catalytic center, whose properties were investigated in this study using a multidisciplinary approach. The [4Fe-3S] cluster undergoes redox-dependent reversible transformations, namely iron swapping between a sulfide and a peptide amide N. Moreover, our investigations unraveled the redox-dependent and reversible occurence of an oxygen ligand located at a different iron. This ligand is hydrogen bonded to a conserved histidine that is essential for H(2) oxidation at high O(2). We propose that these transformations, reminiscent of those of the P-cluster of nitrogenase, enable the consecutive transfer of two electrons within a physiological potential range.

Double-flow focused liquid injector for efficient serial femtosecond crystallography

“…Native Re MBH was expressed and purified in the as-isolated (air-oxidised) state as described elsewhere161727. Re MBH nano- and microcrystals were grown at 4°–6 °C and pH 5.5–6.5 in the presence of 20–30% PEG3350 and Bis-(2-hydroxy-ethyl)-amino-tris(hydroxylmethyl)-methane following the micro-crystallization setup-protocol as described for PYP28.…”

Biohydrogen for a New Generation of H2/O2 Biofuel Cells: A Sustainable Energy Perspective

“…[134] This histidine residue, which is conserved in the majority of O 2 -sensitive and O 2 -tolerant Hases, has also been demonstrated to play a key role in O 2 tolerance in Re MbH. [135] This is definitely not the end of the story. Nevertheless, based on current knowledge (note that very recent results suggest that O 2 could directly bind the proximal cluster), [135] thanks to the unusual FeS proximal cluster, it is proposed that when O 2 reaches the active site, it is immediately reduced by four electrons, producing H 2 O and only the fast reactivating Ni-B state ( Figure 6).…”

“…[135] This is definitely not the end of the story. Nevertheless, based on current knowledge (note that very recent results suggest that O 2 could directly bind the proximal cluster), [135] thanks to the unusual FeS proximal cluster, it is proposed that when O 2 reaches the active site, it is immediately reduced by four electrons, producing H 2 O and only the fast reactivating Ni-B state ( Figure 6). Accordingly, hydrophilic cavities have been identified in the crystal structures of MbH that could serve as a water evacuation route from the active site.…”

Die Brennstoffzelle der Knallgasbakterien

“…5 9) Weitere Anwendungsperspektiven für sauerstoffresistente Hydrogenasen liegen in der Kopplung mit dem Photosystem I der Photosynthese zur Produktion von Solarwasserstoff sowie in der Herstellung von isotopenmarkierten Biomolekülen aus schwerem Wasserstoff. 4)…”