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Architecture of the human mitochondrial iron-sulfur cluster assembly machinery

Gakh, Oleksandr; Ranatunga, Wasantha; Smith, Douglas Y.; Ahlgren, Eva Christina LU ; Al-Karadaghi, Salam LU ; Thompson, James R. and Isaya, Grazia (2016) In Journal of Biological Chemistry 291(40). p.21296-21321
Abstract

Fe-S clusters, essential cofactors needed for the activity of many different enzymes, are assembled by conserved protein machineries inside bacteria and mitochondria. As the architecture of the human machinery remains undefined, we co-expressed in Escherichia coli the following four proteins involved in the initial step of Fe-S cluster synthesis: FXN42-210 (iron donor); [NFS1]·[ISD11] (sulfur donor); and ISCU (scaffold upon which new clusters are assembled). We purified a stable, active complex consisting of all four proteins with 1:1:1:1 stoichiometry. Using negative staining transmission EM and single particle analysis, we obtained a three-dimensional model of the complex with ∼14 Å resolution. Molecular dynamics flexible... (More)

Fe-S clusters, essential cofactors needed for the activity of many different enzymes, are assembled by conserved protein machineries inside bacteria and mitochondria. As the architecture of the human machinery remains undefined, we co-expressed in Escherichia coli the following four proteins involved in the initial step of Fe-S cluster synthesis: FXN42-210 (iron donor); [NFS1]·[ISD11] (sulfur donor); and ISCU (scaffold upon which new clusters are assembled). We purified a stable, active complex consisting of all four proteins with 1:1:1:1 stoichiometry. Using negative staining transmission EM and single particle analysis, we obtained a three-dimensional model of the complex with ∼14 Å resolution. Molecular dynamics flexible fitting of protein structures docked into the EM map of the model revealed a [FXN42-210]24·[NFS1]24·[ISD11]24·[ISCU]24 complex, consistent with the measured 1:1:1:1 stoichiometry of its four components. The complex structure fulfills distance constraints obtained from chemical cross-linking of the complex at multiple recurring interfaces, involving hydrogen bonds, salt bridges, or hydrophobic interactions between conserved residues. The complex consists of a central roughly cubic [FXN42-210]24·[ISCU]24 sub-complex with one symmetric ISCU trimer bound on top of one symmetric FXN42-210 trimer at each of its eight vertices. Binding of 12 [NFS1]2·[ISD11]2 sub-complexes to the surface results in a globular macromolecule with a diameter of ∼15 nm and creates 24 Fe-S cluster assembly centers. The organization of each center recapitulates a previously proposed conserved mechanism for sulfur donation from NFS1 to ISCU and reveals, for the first time, a path for iron donation from FXN42-210 to ISCU.

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author
organization
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type
Contribution to journal
publication status
published
subject
in
Journal of Biological Chemistry
volume
291
issue
40
pages
26 pages
publisher
ASBMB
external identifiers
  • scopus:84988981188
  • wos:000385406200041
ISSN
0021-9258
DOI
10.1074/jbc.M116.738542
language
English
LU publication?
yes
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b738ce02-fa4a-4161-990c-b81ee37a85e7
date added to LUP
2016-10-31 07:56:33
date last changed
2017-11-12 04:25:37
@article{b738ce02-fa4a-4161-990c-b81ee37a85e7,
  abstract     = {<p>Fe-S clusters, essential cofactors needed for the activity of many different enzymes, are assembled by conserved protein machineries inside bacteria and mitochondria. As the architecture of the human machinery remains undefined, we co-expressed in Escherichia coli the following four proteins involved in the initial step of Fe-S cluster synthesis: FXN<sup>42-210</sup> (iron donor); [NFS1]·[ISD11] (sulfur donor); and ISCU (scaffold upon which new clusters are assembled). We purified a stable, active complex consisting of all four proteins with 1:1:1:1 stoichiometry. Using negative staining transmission EM and single particle analysis, we obtained a three-dimensional model of the complex with ∼14 Å resolution. Molecular dynamics flexible fitting of protein structures docked into the EM map of the model revealed a [FXN<sup>42-210</sup>]<sub>24</sub>·[NFS1]<sub>24</sub>·[ISD11]<sub>24</sub>·[ISCU]<sub>24</sub> complex, consistent with the measured 1:1:1:1 stoichiometry of its four components. The complex structure fulfills distance constraints obtained from chemical cross-linking of the complex at multiple recurring interfaces, involving hydrogen bonds, salt bridges, or hydrophobic interactions between conserved residues. The complex consists of a central roughly cubic [FXN<sup>42-210</sup>]<sub>24</sub>·[ISCU]<sub>24</sub> sub-complex with one symmetric ISCU trimer bound on top of one symmetric FXN<sup>42-210</sup> trimer at each of its eight vertices. Binding of 12 [NFS1]<sub>2</sub>·[ISD11]<sub>2</sub> sub-complexes to the surface results in a globular macromolecule with a diameter of ∼15 nm and creates 24 Fe-S cluster assembly centers. The organization of each center recapitulates a previously proposed conserved mechanism for sulfur donation from NFS1 to ISCU and reveals, for the first time, a path for iron donation from FXN<sup>42-210</sup> to ISCU.</p>},
  author       = {Gakh, Oleksandr and Ranatunga, Wasantha and Smith, Douglas Y. and Ahlgren, Eva Christina and Al-Karadaghi, Salam and Thompson, James R. and Isaya, Grazia},
  issn         = {0021-9258},
  language     = {eng},
  month        = {09},
  number       = {40},
  pages        = {21296--21321},
  publisher    = {ASBMB},
  series       = {Journal of Biological Chemistry},
  title        = {Architecture of the human mitochondrial iron-sulfur cluster assembly machinery},
  url          = {http://dx.doi.org/10.1074/jbc.M116.738542},
  volume       = {291},
  year         = {2016},
}