Physiologically relevant reconstitution of iron-sulfur cluster biosynthesis uncovers persulfide-processing functions of ferredoxin-2 and frataxin

Nat Commun. 2019 Aug 8;10(1):3566. doi: 10.1038/s41467-019-11470-9.

Abstract

Iron-sulfur (Fe-S) clusters are essential protein cofactors whose biosynthetic defects lead to severe diseases among which is Friedreich's ataxia caused by impaired expression of frataxin (FXN). Fe-S clusters are biosynthesized on the scaffold protein ISCU, with cysteine desulfurase NFS1 providing sulfur as persulfide and ferredoxin FDX2 supplying electrons, in a process stimulated by FXN but not clearly understood. Here, we report the breakdown of this process, made possible by removing a zinc ion in ISCU that hinders iron insertion and promotes non-physiological Fe-S cluster synthesis from free sulfide in vitro. By binding zinc-free ISCU, iron drives persulfide uptake from NFS1 and allows persulfide reduction into sulfide by FDX2, thereby coordinating sulfide production with its availability to generate Fe-S clusters. FXN stimulates the whole process by accelerating persulfide transfer. We propose that this reconstitution recapitulates physiological conditions which provides a model for Fe-S cluster biosynthesis, clarifies the roles of FDX2 and FXN and may help develop Friedreich's ataxia therapies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbon-Sulfur Lyases / metabolism
  • Ferredoxins / isolation & purification
  • Ferredoxins / metabolism*
  • Friedreich Ataxia / pathology
  • Iron / metabolism
  • Iron-Binding Proteins / isolation & purification
  • Iron-Binding Proteins / metabolism*
  • Iron-Sulfur Proteins / chemistry
  • Iron-Sulfur Proteins / genetics
  • Iron-Sulfur Proteins / metabolism*
  • Mutagenesis, Site-Directed
  • Nuclear Magnetic Resonance, Biomolecular
  • Oxidation-Reduction
  • Proton Magnetic Resonance Spectroscopy
  • Recombinant Proteins / genetics
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / metabolism
  • Sulfides / metabolism*
  • Zinc / metabolism

Substances

  • FDX2 protein, human
  • Ferredoxins
  • ISCU protein, human
  • Iron-Binding Proteins
  • Iron-Sulfur Proteins
  • IscU protein, mouse
  • Recombinant Proteins
  • Sulfides
  • frataxin
  • persulfides
  • Iron
  • Carbon-Sulfur Lyases
  • NFS1 protein, human
  • Nfs1 protein, mouse
  • Zinc