文章基本信息

标题：Tracking the route of molecular oxygen in O2-tolerant membrane-bound [NiFe] hydrogenase
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作者：Jacqueline Kalms ; Andrea Schmidt ; Stefan Frielingsdorf 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2018
卷号：115
期号：10
页码：E2229-E2237
DOI：10.1073/pnas.1712267115
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：[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.
关键词：oxygen-tolerant [NiFe] hydrogenase ; metalloproteins ; iron–sulfur cluster ; X-ray crystallography ; crystal derivatization