April 2009
Volume 50, Issue 13
ARVO Annual Meeting Abstract  |   April 2009
Apoferritin Is Maintaining the Native Conformation of Citrate Synthase in vitro
Author Affiliations & Notes
  • Y. V. Sergeev
    OGVFB, NEI/NIH, Bethesda, Maryland
  • J. F. Hejtmancik
    OGVFB, NEI/NIH, Bethesda, Maryland
  • Footnotes
    Commercial Relationships  Y.V. Sergeev, None; J.F. Hejtmancik, None.
  • Footnotes
    Support  None.
Investigative Ophthalmology & Visual Science April 2009, Vol.50, 3402. doi:
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      Y. V. Sergeev, J. F. Hejtmancik; Apoferritin Is Maintaining the Native Conformation of Citrate Synthase in vitro. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3402.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: : Ferritin, a member of family of iron storage proteins, is found in a wide variety of different human tissues including cornea, retina and RPE. Ferritin has been shown to increase in response to stress and inflammation and to sequester iron-II in the cell. In the eye rising levels of ferritin were detected in hyper-ferritinemia cataract and age-related macular degeneration. Ferritin expression under oxidative or temperature stress conditions and its protective effect on cell viability suggest that ferritin lacking iron (apoferritin) may have a role in the formation, stabilization or maintenance of the native conformation of proteins.

Methods: : To test this hypothesis we studied the influence of apoferritin on the unfolding and refolding of citrate synthase (CS) in vitro using aggregation assay, size exclusion chromatography, SDS-PAGE and Western blot analysis, and fluorescent spectroscopy. The native state of CS was determined by measuring catalytic activity.

Results: : Here we show that at stoichiometric amounts apoferritin protects CS catalytic activity, stabilize the aggregation of CS under heat stress,and acts as a chaperone-like molecule in these folding reactions in vitro. Furthermore, apoferritin promotes the functional refolding of CS after guanidinium hydrochloride denaturation. Experiments on biotin label transfer demonstrated that iron-free apoferritin participates in transient protein-protein interactions with protein substrates, whereas ferritin does not show this interaction.

Conclusions: : These results confirm that apoferritin has chaperone-like activity in vitro and suggests that in addition to its iron binding activity apoferritin might have a role in protecting and maintaining the native conformation of proteins in the eye.

Keywords: protein structure/function • chaperones • stress response 

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