H-Cluster Assembly Intermediates Built on HydF by the Radical SAM Enzymes HydE and HydG

Amanda S. Byer, Eric M. Shepard, Michael W. Ratzloff, Jeremiah N. Betz, Paul W. King, William E. Broderick, Joan B. Broderick

Research output: Contribution to journalArticlepeer-review

14 Scopus Citations

Abstract

Abstract: [FeFe]-hydrogenase catalyzes the reversible reduction of protons to H2 at a complex metallocofactor site, the H-cluster. Biosynthesis of this active-site H-cluster requires three maturation enzymes: the radical S-adenosylmethionine enzymes HydE and HydG synthesize the nonprotein ligands, while the GTPase HydF provides a scaffold for assembly of the 2Fe subcluster of the H-cluster ([2Fe]H) prior to its transfer to hydrogenase. To delineate the assembly and delivery steps for the 2Fe precursor cluster coordinated to HydF ([2Fe]F), we have heterologously expressed HydF in the presence of HydE alone (HydFE) or HydG alone (HydFG), and characterized the resulting purified HydFE and HydFG using UV–visible, EPR, and FTIR spectroscopies and biochemical assays. The iron–sulfur clusters on HydF are modified by co-expression with HydE or HydG, as evidenced by the changes in the visible, EPR, and FTIR spectral features. Further, biochemical assays show that HydFE is capable of activating HydAΔEFG to a limited extent (~ 1% of WT) even though the normal source of CO and CN ligands of [2Fe]H (HydG) was absent. Activation assays performed with HydFG, in contrast, exhibit no ability to mature HydAΔEFG. It appears that in the case of HydFE, trace diatomics from the cellular environment are incorporated into a [2Fe]F-like precursor on HydF in the absence of HydG. We conclude that the product of HydE, presumably the dithiomethylamine ligand of [2Fe]H, is absolutely essential to the activation process, while the diatomic products of HydG can be provided from alternate sources. Graphic abstract: [Figure not available: see fulltext.].

Original languageAmerican English
Pages (from-to)783-792
Number of pages10
JournalJournal of Biological Inorganic Chemistry
Volume24
Issue number6
DOIs
StatePublished - 2019

Bibliographical note

Publisher Copyright:
© 2019, Society for Biological Inorganic Chemistry (SBIC).

NREL Publication Number

  • NREL/JA-2700-74929

Keywords

  • Biosynthesis
  • H-cluster
  • HydF
  • Maturation
  • Radical SAM
  • [FeFe] hydrogenase

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