The single-particle structures of a Bacterial Cyanide Dihydratase and a Fungal Cyanide Hydratase

Cyanide is widely used in industries due to its strong affinity for metals, a property that also underlies its potent toxicity. Industries therefore must reduce cyanide concentration in wastewater final disposal. Physical, chemical, and biological methods have been developed for this purpose; however, knowledge about the structure of enzymes involved in cyanide degradation remains limited. Structural characterization of these proteins could facilitate the development of more efficient enzymes with enhanced bioremediation potential. Here, we present the single-particle cryo-electron microscopy structures of a cyanide dihydratase from Bacillus safensis and a cyanide hydratase from Gloeocercospora sorghi at 2.2 [A] and 2.0 [A] resolution, respectively. We provide a comprehensive description and comparative analysis of these structures alongside all previously experimentally determined nitrilase structures. Importantly, our full-length structures reveal new structural features in the C-terminal as well as specific intermolecular interactions between protomer interfaces and within the helix lumen. Finally, our findings offer insights into the possible reaction mechanisms of these two enzymes.