Structural characterization of metal binding to a cold-adapted frataxin
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Frataxin is an evolutionary conserved protein that participates in iron metabolism. Deficiency of this small protein in humans causes a severe neurodegenerative disease known as Friedreich’s ataxia. A number of studies indicate that frataxin binds iron and regulates Fe–S cluster biosynthesis. Previous structural studies showed that metal binding occurs mainly in a region of high density of negative charge. However, a comprehensive characterization of the binding sites is required to gain further insights into the mechanistic details of frataxin function. In this work, we have solved the X-ray crystal structures of a cold-adapted frataxin from a psychrophilic bacterium in the presence of cobalt or europium ions. We have identified a number of metal-binding sites, mainly solvent exposed, several of which had not been observed in previous studies on mesophilic homologues. No major structural changes were detected upon metal binding, although the structures exhibit significant changes in crystallographic B-factors. The analysis of these B-factors, in combination with crystal packing and RMSD among structures, suggests the existence of localized changes in the internal motions. Based on these results, we propose that bacterial frataxins possess binding sites of moderate affinity for a quick capture and transfer of iron to other proteins and for the regulation of Fe–S cluster biosynthesis, modulating interactions with partner proteins.
KeywordsCyaY protein family Iron binding X-ray diffraction Conformational dynamics Extremophile
This work was supported by the Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT), the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires (UBACyT), the CNRS, the INSERM, the Université de Strasbourg, the Région Alsace, the Hôpital Civil de Strasbourg, Instruct [part of the European Strategy Forum of Research Infrastructures (ESFRI)] and the French Infrastructure for Integrated Structural Biology (FRISBI) ANR-10-INSB-05-01. We specially thank the IGBMC Structural Genomics Platform staff (in particular, Pierre Poussin Courmontagne and Dr. Alastair McEwen). The crystallographic experiments were performed on the X06DA beamline at the Swiss Light Source, Paul Scherrer Institut, Villigen, Switzerland. In particular, we thank Christian Stirnimann and Vincent Olieric for their help on the beamline.
- 25.Adams PD, Afonine PV, Bunkoczi G, Chen VB, Davis IW, Echols N, Headd JJ, Hung LW, Kapral GJ, Grosse-Kunstleve RW, McCoy AJ, Moriarty NW, Oeffner R, Read RJ, Richardson DC, Richardson JS, Terwilliger TC, Zwart PH (2010) Acta Crystallogr D Biol Crystallogr 66:213–221CrossRefPubMedCentralPubMedGoogle Scholar
- 33.Sawyer WH, Winzor DJ (2001) Curr Protoc Protein Sci 16:5A:A.5A.1–A.5A.40Google Scholar