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Bacterial frataxin CyaY is the gatekeeper of iron-sulfur cluster formation catalyzed by IscS

Nature Structural & Molecular Biology volume 16, pages 390–396 (2009)Cite this article

Abstract

Frataxin is an essential mitochondrial protein whose reduced expression causes Friedreich's ataxia (FRDA), a lethal neurodegenerative disease. It is believed that frataxin is an iron chaperone that participates in iron metabolism. We have tested this hypothesis using the bacterial frataxin ortholog, CyaY, and different biochemical and biophysical techniques. We observe that CyaY participates in iron-sulfur (Fe-S) cluster assembly as an iron-dependent inhibitor of cluster formation, through binding to the desulfurase IscS. The interaction with IscS involves the iron binding surface of CyaY, which is conserved throughout the frataxin family. We propose that frataxins are iron sensors that act as regulators of Fe-S cluster formation to fine-tune the quantity of Fe-S cluster formed to the concentration of the available acceptors. Our observations provide new perspectives for understanding FRDA and a mechanistic model that rationalizes the available knowledge on frataxin.

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Figure 1: Fe-S cluster reconstitution on IscU followed by absorbance and CD measurements.
Figure 2: Dissecting the pathway of cluster reconstitution in the absence and in the presence of CyaY.
Figure 3: Interaction of CyaY with IscS.
Figure 4: The effect of iron and CyaY concentration on the kinetics of Fe-S cluster formation.
Figure 5: Gel-filtration profiles to test the state of aggregation of CyaY under the conditions used for cluster reconstitution.
Figure 6: Schematic model of the molecular mechanism of frataxin in the cell.

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Acknowledgements

We dedicate this work to the memory of Margie Nair. We are thankful to R.A.G. Williams, F. Foury, M. Pandolfo and H. Puccio for stimulating discussions, P. Temussi for moral support, L. Temussi for technical discussions and the Mill Hill NMR Centre for technical support. The project was supported by PUR funds (F.B. and S.I., University of Milan).

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Author notes

  1. Annalisa Pastore

    Present address: Temporary address: Unité de Virologie et Immunologies Moéculaire, Intitut National de la Recherché Agronomique, Jouy-en-Josas, France.,

  2. Chiara Pastore

    Present address: Present address: Department of Biological Sciences, Columbia University, New York, New York, USA.,

Authors and Affiliations

  1. National Institute for Medical Research, The Ridgeway, London, UK

    Salvatore Adinolfi, Clara Iannuzzi, Filippo Prischi, Chiara Pastore, Stephen R Martin & Annalisa Pastore

  2. Dipartimento di Biochimica e Biofisica, II Universita' degli Studi di Napoli, Napoli, Italy

    Clara Iannuzzi

  3. Dipartimento di Biologia Molecolare, University of Siena, Siena, Italy

    Filippo Prischi

  4. DISMA, University of Milan, Milan, Italy

    Stefania Iametti & Franco Bonomi

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Correspondence to Annalisa Pastore.

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Adinolfi, S., Iannuzzi, C., Prischi, F. et al. Bacterial frataxin CyaY is the gatekeeper of iron-sulfur cluster formation catalyzed by IscS. Nat Struct Mol Biol 16, 390–396 (2009). https://doi.org/10.1038/nsmb.1579

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