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Proc Natl Acad Sci U S A. 2018 Mar 6;115(10):E2229-E2237. doi: 10.1073/pnas.1712267115. Epub 2018 Feb 20.

Tracking the route of molecular oxygen in O2-tolerant membrane-bound [NiFe] hydrogenase.

Author information

1
Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Institute of Medical Physics and Biophysics, Group Protein X-ray Crystallography and Signal Transduction, D-10117 Berlin, Germany.
2
Institut für Chemie, Technische Universität Berlin, D-10623 Berlin, Germany.
3
European Synchrotron Radiation Facility, F-38043 Grenoble, France.
4
Partnership for Soft Condensed Matter (PSCM), F-38043 Grenoble, France.
5
Univ. Grenoble Alpes, CNRS, CEA, Institut de Biologie Structurale (IBS), F-38000 Grenoble, France.
6
Univ. Grenoble Alpes, CNRS, CEA, Institut de Biosciences et Biotechnologies de Grenoble (BIG)-Laboratoire Chimie et Biologie des Métaux (LCBM), F-38000 Grenoble, France.
7
Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Institute of Medical Physics and Biophysics, Group Protein X-ray Crystallography and Signal Transduction, D-10117 Berlin, Germany; patrick.scheerer@charite.de.

Abstract

[NiFe] hydrogenases catalyze the reversible splitting of H2 into protons and electrons at a deeply buried active site. The catalytic center can be accessed by gas molecules through a hydrophobic tunnel network. While most [NiFe] hydrogenases are inactivated by O2, a small subgroup, including the membrane-bound [NiFe] hydrogenase (MBH) of Ralstonia eutropha, is able to overcome aerobic inactivation by catalytic reduction of O2 to water. This O2 tolerance relies on a special [4Fe3S] cluster that is capable of releasing two electrons upon O2 attack. Here, the O2 accessibility of the MBH gas tunnel network has been probed experimentally using a "soak-and-freeze" derivatization method, accompanied by protein X-ray crystallography and computational studies. This combined approach revealed several sites of O2 molecules within a hydrophobic tunnel network leading, via two tunnel entrances, to the catalytic center of MBH. The corresponding site occupancies were related to the O2 concentrations used for MBH crystal derivatization. The examination of the O2-derivatized data furthermore uncovered two unexpected structural alterations at the [4Fe3S] cluster, which might be related to the O2 tolerance of the enzyme.

KEYWORDS:

X-ray crystallography; crystal derivatization; iron–sulfur cluster; metalloproteins; oxygen-tolerant [NiFe] hydrogenase

PMID:
29463722
PMCID:
PMC5877991
DOI:
10.1073/pnas.1712267115
[Indexed for MEDLINE]
Free PMC Article

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