Biosynthesis of the FeFe hydrogenase active site

Abstract

FeFe hydrogenases catalyze the reversible interconversion of H 2 with protons and electrons, and thereby provide either an electron source or an electron sink for a variety of metabolic processes. Hydrogenase reactivity occurs at the H cluster which consists of a conventional [4Fe–4S] H subcluster bridged via a cysteine residue to an unusual organometallic [2Fe] H subcluster. The mechanism of H‐cluster bioassembly has emerged as an active topic of research that presents fresh challenges in the coordination chemistry, radical chemistry, and biochemistry of Fe‐S enzymes and is also important for developing biotechnological systems for solar fuels production. Our work in this area focuses on the radical SAM enzyme HydG, one of three maturase enzymes that build the organometallic [2Fe] H subcluster. HydG's role is particularly important because it transforms inorganic Fe 2+ into an organometallic [Fe(CO) 2 (CN)] species that eventually comprises the [2Fe] H subcluster. Our work concerns the characterization of this and related organometallic intermediates with an emphasis on the mechanisms of their formation.