SAXS and stability studies of iron-induced oligomers of bacterial frataxin CyaY

Mostafa Fekry, Wessen Alshokry, Przemysław Grela, Marek Tchórzewski, Eva Christina Ahlgren, Christopher A. Söderberg, Oleksandr Gakh, Grazia Isaya, Salam Al-Karadaghi

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Abstract

Frataxin is a highly conserved protein found in both prokaryotes and eukaryotes. It is involved in several central functions in cells, which include iron delivery to biochemical processes, such as heme synthesis, assembly of iron-sulfur clusters (ISC), storage of surplus iron in conditions of iron overload, and repair of ISC in aconitase. Frataxin from different organisms has been shown to undergo iron-dependent oligomerization. At least two different classes of oligomers, with different modes of oligomer packing and stabilization, have been identified. Here, we continue our efforts to explore the factors that control the oligomerization of frataxin from different organisms, and focus on E. coli frataxin CyaY. Using small-angle X-ray scattering (SAXS), we show that higher iron-to-protein ratios lead to larger oligomeric species, and that oligomerization proceeds in a linear fashion as a results of iron oxidation. Native mass spectrometry and online size-exclusion chromatography combined with SAXS show that a dimer is the most common form of CyaY in the presence of iron at atmospheric conditions. Modeling of the dimer using the SAXS data confirms the earlier proposed head-to-tail packing arrangement of monomers. This packing mode brings several conserved acidic residues into close proximity to each other, creating an environment for metal ion binding and possibly even mineralization. Together with negative-stain electron microscopy, the experiments also show that trimers, tetramers, pentamers, and presumably higher-order oligomers may exist in solution. Nano-differential scanning fluorimetry shows that the oligomers have limited stability and may easily dissociate at elevated temperatures. The factors affecting the possible oligomerization mode are discussed.

Original languageEnglish (US)
Pages (from-to)e0184961
JournalPLoS One
Volume12
Issue number9
DOIs
StatePublished - 2017

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X ray scattering
Oligomers
X-radiation
Iron
X-Rays
iron
Oligomerization
Sulfur
Dimers
sulfur
Biochemical Phenomena
Aconitate Hydratase
aconitate hydratase
iron overload
Fluorometry
fluorometry
Iron Overload
frataxin
organisms
heme

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)

Cite this

Fekry, M., Alshokry, W., Grela, P., Tchórzewski, M., Ahlgren, E. C., Söderberg, C. A., ... Al-Karadaghi, S. (2017). SAXS and stability studies of iron-induced oligomers of bacterial frataxin CyaY. PLoS One, 12(9), e0184961. https://doi.org/10.1371/journal.pone.0184961

SAXS and stability studies of iron-induced oligomers of bacterial frataxin CyaY. / Fekry, Mostafa; Alshokry, Wessen; Grela, Przemysław; Tchórzewski, Marek; Ahlgren, Eva Christina; Söderberg, Christopher A.; Gakh, Oleksandr; Isaya, Grazia; Al-Karadaghi, Salam.

In: PLoS One, Vol. 12, No. 9, 2017, p. e0184961.

Research output: Contribution to journalArticle

Fekry, M, Alshokry, W, Grela, P, Tchórzewski, M, Ahlgren, EC, Söderberg, CA, Gakh, O, Isaya, G & Al-Karadaghi, S 2017, 'SAXS and stability studies of iron-induced oligomers of bacterial frataxin CyaY', PLoS One, vol. 12, no. 9, pp. e0184961. https://doi.org/10.1371/journal.pone.0184961
Fekry M, Alshokry W, Grela P, Tchórzewski M, Ahlgren EC, Söderberg CA et al. SAXS and stability studies of iron-induced oligomers of bacterial frataxin CyaY. PLoS One. 2017;12(9):e0184961. https://doi.org/10.1371/journal.pone.0184961
Fekry, Mostafa ; Alshokry, Wessen ; Grela, Przemysław ; Tchórzewski, Marek ; Ahlgren, Eva Christina ; Söderberg, Christopher A. ; Gakh, Oleksandr ; Isaya, Grazia ; Al-Karadaghi, Salam. / SAXS and stability studies of iron-induced oligomers of bacterial frataxin CyaY. In: PLoS One. 2017 ; Vol. 12, No. 9. pp. e0184961.
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