Direct Observation of an Iron-Bound Terminal Hydride in [FeFe]-Hydrogenase by Nuclear Resonance Vibrational Spectroscopy

J Am Chem Soc. 2017 Mar 29;139(12):4306-4309. doi: 10.1021/jacs.7b00686. Epub 2017 Mar 20.

Abstract

[FeFe]-hydrogenases catalyze the reversible reduction of protons to molecular hydrogen with extremely high efficiency. The active site ("H-cluster") consists of a [4Fe-4S]H cluster linked through a bridging cysteine to a [2Fe]H subsite coordinated by CN- and CO ligands featuring a dithiol-amine moiety that serves as proton shuttle between the protein proton channel and the catalytic distal iron site (Fed). Although there is broad consensus that an iron-bound terminal hydride species must occur in the catalytic mechanism, such a species has never been directly observed experimentally. Here, we present FTIR and nuclear resonance vibrational spectroscopy (NRVS) experiments in conjunction with density functional theory (DFT) calculations on an [FeFe]-hydrogenase variant lacking the amine proton shuttle which is stabilizing a putative hydride state. The NRVS spectra unequivocally show the bending modes of the terminal Fe-H species fully consistent with widely accepted models of the catalytic cycle.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Hydrogenase / chemistry*
  • Hydrogenase / metabolism
  • Iron / chemistry*
  • Iron / metabolism
  • Iron-Sulfur Proteins / chemistry*
  • Iron-Sulfur Proteins / metabolism
  • Magnetic Resonance Spectroscopy
  • Molecular Conformation
  • Quantum Theory
  • Spectroscopy, Fourier Transform Infrared
  • Water / chemistry
  • Water / metabolism

Substances

  • Iron-Sulfur Proteins
  • Water
  • Iron
  • iron hydrogenase
  • Hydrogenase