Spectroscopic Characterization of the Bridging Amine in the Active Site of [FeFe] Hydrogenase Using Isotopologues of the H-Cluster

J Am Chem Soc. 2015 Oct 14;137(40):12744-7. doi: 10.1021/jacs.5b06240. Epub 2015 Sep 29.


The active site of [FeFe] hydrogenase contains a catalytic binuclear iron subsite coordinated by CN(-) and CO ligands as well as a unique azadithiolate (adt(2-)) bridging ligand. It has been established that this binuclear cofactor is synthesized and assembled by three maturation proteins HydE, -F, and -G. By means of in vitro maturation in the presence of (15)N- and (13)C-labeled tyrosine it has been shown that the CN(-) and CO ligands originate from tyrosine. The source of the bridging adt(2-) ligand, however, remains unknown. In order to identify the nitrogen of the bridging amine using HYSCORE spectroscopy and distinguish its spectroscopic signature from that of the CN(-) nitrogens, we studied three isotope-labeled variants of the H-cluster ((15)N-adt(2-)/C(14)N(-), (15)N-adt(2-)/C(15)N(-), and (14)N-adt(2-)/C(15)N(-)) and extracted accurate values of the hyperfine and quadrupole couplings of both CN(-) and adt(2-) nitrogens. This will allow an evaluation of isotopologues of the H-cluster generated by in vitro bioassembly in the presence of various (15)N-labeled potential precursors as possible sources of the bridging ligand.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amines / chemistry*
  • Catalytic Domain
  • Hydrogen / chemistry*
  • Hydrogenase / chemistry*
  • Iron-Sulfur Proteins / chemistry*


  • Amines
  • Iron-Sulfur Proteins
  • Hydrogen
  • iron hydrogenase
  • Hydrogenase