Going beyond Structure: Nickel-Substituted Rubredoxin as a Mechanistic Model for the [NiFe] Hydrogenases

• DOI: 10.1021/jacs.8b05194
• Publication Date: 2018-07-18T16:13:14Z
• Authors: Jeffrey W. Slater; Sean C. Marguet; Haleigh A. Monaco; Hannah S. Shafaat
• Keywords: Rubredoxin; Hydrogenase

Well-defined molecular systems for catalytic hydrogen production that are robust, easily generated, and active under mild aqueous conditions remain underdeveloped. Nickel-substituted rubredoxin (NiRd) is one such system, featuring a tetrathiolate coordination environment around the nickel center identical to native [NiFe] hydrogenases demonstrating hydrogenase-like proton reduction activity. However, until now, mechanism has remained elusive. In this work, we have combined quantitative protein film electrochemistry with optical vibrational spectroscopy, density functional theory calculations, dynamics simulations interrogate of H2 evolution by NiRd. Proton-coupled electron transfer found be essential catalysis. The coordinating thiolate ligands serve as sites protonation, role remains debated in hydrogenases, occurring at following protonation. rate-determining step suggested intramolecular via thiol inversion generate NiIII–hydride species. NiRd catalysis completely insensitive presence oxygen, another advantage over hydrogenase enzymes, potential implications membrane-less fuel cells aerobic evolution. Targeted mutations metal seen increase activity perturb process, highlighting importance outer sphere. Collectively, these results indicate evolves through similar suggesting protonation enzyme guiding rational optimization system.