Converting a cysteine-rich natively noncatalytic protein to an artificial hydrogenase.

An artificial hydrogenase is constructed when the natively noncatalytic α-domain of the Cys-rich protein metallothionein (MT) is assembled with Ni II . αMT binds four eq. of Ni II in a non-cooperative manner where the addition of the 1 st Ni II eq. affords the most catalytically active species with little effect on photocatalytic H 2 production during subsequent metal addition. The critical role of protonated Cys residue(s) in H-H bond formation is demonstrated.