X-ray Crystallography and Vibrational Spectroscopy Reveal the Key Determinants of Biocatalytic Dihydrogen Cycling by [NiFe] Hydrogenases.

[NiFe] hydrogenases are complex model enzymes for the reversible cleavage of dihydrogen (H ₂ ). However, structural determinants of efficient H ₂ binding to their [NiFe] active site are not properly understood. Here, we present crystallographic and vibrational-spectroscopic insights into the unexplored structure of the H ₂ -binding [NiFe] intermediate. Using an F ₄₂₀ -reducing [NiFe]-hydrogenase from Methanosarcina barkeri as a model enzyme, we show that the protein backbone provides a strained chelating scaffold that tunes the [NiFe] active site for efficient H ₂ binding and conversion. The protein matrix also directs H ₂ diffusion to the [NiFe] site via two gas channels and allows the distribution of electrons between functional protomers through a subunit-bridging FeS cluster. Our findings emphasize the relevance of an atypical Ni coordination, thereby providing a blueprint for the design of bio-inspired H ₂ -conversion catalysts.
(© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)