[FeFe]-hydrogenases catalyze the conversion of protons and electrons to molecular hydrogen, but upon exposure to oxygen, their catalytic cofactor is irreversibly inactivated. Here, the authors determine the crystal structure of hydrogenase CbA5H and identify a cysteine residue, which acts as a safety cap that shields the active site from oxygen.
- Martin Winkler
- Jifu Duan
- Thomas Happe
