Crystal Structure of the [FeFe]-Hydrogenase Maturase HydE Bound to Complex-B

J Am Chem Soc. 2021 Jun 9;143(22):8499-8508. doi: 10.1021/jacs.1c03367. Epub 2021 May 28.


[FeFe]-hydrogenases use a unique organometallic complex, termed the H cluster, to reversibly convert H2 into protons and low-potential electrons. It can be best described as a [Fe4S4] cluster coupled to a unique [2Fe]H center where the reaction actually takes place. The latter corresponds to two iron atoms, each of which is bound by one CN- ligand and one CO ligand. The two iron atoms are connected by a unique azadithiolate molecule (-S-CH2-NH-CH2-S-) and an additional bridging CO. This [2Fe]H center is built stepwise thanks to the well-orchestrated action of maturating enzymes that belong to the Hyd machinery. Among them, HydG converts l-tyrosine into CO and CN- to produce a unique l-cysteine-Fe(CO)2CN species termed complex-B. Very recently, HydE was shown to perform radical-based chemistry using synthetic complex-B as a substrate. Here we report the high-resolution crystal structure that establishes the identity of the complex-B-bound HydE. By triggering the reaction prior to crystallization, we trapped a new five-coordinate Fe species, supporting the proposal that HydE performs complex modifications of complex-B to produce a monomeric "SFe(CO)2CN" precursor to the [2Fe]H center. Substrate access, product release, and intermediate transfer are also discussed.

Publication types

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

MeSH terms

  • Hydrogenase / chemistry*
  • Hydrogenase / metabolism
  • Iron-Sulfur Proteins / chemistry*
  • Iron-Sulfur Proteins / metabolism
  • Models, Molecular
  • Protein Conformation


  • Iron-Sulfur Proteins
  • iron hydrogenase
  • Hydrogenase