Two ligand-binding sites in CO-reducing V nitrogenase reveal a general mechanistic principle.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 34049880.
- Also identified by DOI 10.1126/sciadv.abg4474 and PMC identifier 8163085.
- Licence recorded as CC BY-NC.
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Abstract
Besides its role in biological nitrogen fixation, vanadium-containing nitrogenase also reduces carbon monoxide (CO) to hydrocarbons, in analogy to the industrial Fischer-Tropsch process. The protein yields 93% of ethylene (C<sub>2</sub>H<sub>4</sub>), implying a C-C coupling step that mandates the simultaneous binding of two CO at the active site FeV cofactor. Spectroscopic data indicated multiple CO binding events, but structural analyses of Mo and V nitrogenase only confirmed a single site. Here, we report the structure of a two CO-bound state of V nitrogenase at 1.05 Å resolution, with one μ-bridging and one terminal CO molecule. This additional, specific ligand binding site suggests a mechanistic route for CO reduction and hydrocarbon formation, as well as a second access pathway for protons required during the reaction. Moreover, carbonyls are strong-field ligands that are chemically similar to mechanistically relevant hydrides that may be formed and used in a fully analogous fashion.