A model of efficient hydrogen production

[FeFe]-hydrogenases are metalloenzymes involved in microbial energy metabolism in various bacteria and algae, capable of extremes of catalytic performance that would be extremely useful if translated into a means of producing and using hydrogen in fuel cells. In these enzymes catalysis occurs at a unique di-iron centre containing a bridging dithiolate ligand, three CO ligands and two CN⁻ ligands. In this manuscript, the authors show that three synthetic mimics of this di-iron centre can be loaded onto the [FeFe]-hydrogenase maturation protein HydF and then transferred to the algal variant apo-HydA1. Full activation of HydA1 was achieved only with the HydF hybrid protein that contained the mimic with an azadithiolate bridge, confirming the presence of this ligand in the active site of native [FeFe]-hydrogenases. This is the first example of controlled metalloenzyme activation using the combination of a specific protein scaffold and active-site synthetic analogues.