[FeFe]-Hydrogenases: Structure, Mechanism, and Metallocluster Biosynthesis

[FeFe]-hydrogenases catalyzes the reversible conversion of hydrogen into protons and electrons with astonishing efficiency. The reaction occurs at the H-cluster, which is unique in biology. It consists of an organometallic [2Fe]-subcluster bound to a classical [4Fe 4S] cluster by a single cysteine bridging ligand. This book chapter will describe the structure and mechanism of [FeFe]-hydrogenases and focus on recent developments on [FeFe]-hydrogenase maturation, leading to the assembly of the [2Fe]-subcluster, which have revealed a remarkably complex pattern of mostly novel biochemical reactions. This chemical process depends on the concerted action of three metalloproteins. Two radical-SAM enzymes HydE and HydG and a scaffold iron-sulfur containing protein, HydF.