title: Structural characterization of metal binding to a cold-adapted frataxin.
abstract: 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.
authors.affiliation: Instituto de Química y Físico-Química Biológicas, Universidad de Buenos Aires, Junín 956, 1113AAD, Buenos Aires, Argentina.
authors.forename: Martín E
authors.initials: ME
authors.lastname: Noguera
authors.forename: Ernesto A
authors.initials: EA
authors.lastname: Roman
authors.forename: Juan B
authors.initials: JB
authors.lastname: Rigal
authors.forename: Alexandra
authors.initials: A
authors.lastname: Cousido-Siah
authors.forename: André
authors.initials: A
authors.lastname: Mitschler
authors.forename: Alberto
authors.initials: A
authors.lastname: Podjarny
authors.forename: Javier
authors.initials: J
authors.lastname: Santos
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D003035:Cobalt / Q000737:chemistry; D003080:Cold Temperature; D018360:Crystallography, X-Ray; D005063:Europium / Q000737:chemistry; D020563:Gammaproteobacteria / Q000737:chemistry*; D057446:Hydrodynamics; D007501:Iron / Q000737:chemistry*; D033862:Iron-Binding Proteins / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D016415:Sequence Alignment; D000096923:Frataxin
chemical_list: D003035:Cobalt; D005063:Europium; D007501:Iron; D033862:Iron-Binding Proteins; D000096923:Frataxin
references.citation: Biochem J. 2010 Feb 09;426(2):197-203
references.pmid: 20001966
references.citation: PLoS One. 2012;7(9):e45743
references.pmid: 23049850
references.citation: Proteins. 2010 May 15;78(7):1724-35
references.pmid: 20186973
references.citation: Arch Biochem Biophys. 2007 Jan 1;457(1):111-22
references.pmid: 17098208
references.citation: Biochemistry. 2004 Dec 28;43(51):16254-62
references.pmid: 15610019
references.citation: J Appl Crystallogr. 2007 Aug 1;40(Pt 4):658-674
references.pmid: 19461840
references.citation: Acta Crystallogr D Biol Crystallogr. 2010 Jan;66(Pt 1):12-21
references.pmid: 20057044
references.citation: J Neurochem. 2013 Aug;126 Suppl 1:43-52
references.pmid: 23859340
references.citation: Acta Crystallogr D Biol Crystallogr. 2006 Jun;62(Pt 6):569-75
references.pmid: 16699182
references.citation: Structure. 2006 Oct;14(10):1535-46
references.pmid: 17027502
references.citation: Nat Protoc. 2014 Jan;9(1):156-70
references.pmid: 24356774
references.citation: Crit Rev Biochem Mol Biol. 2006 Sep-Oct;41(5):269-91
references.pmid: 16911956
references.citation: Acta Crystallogr D Biol Crystallogr. 2011 Apr;67(Pt 4):235-42
references.pmid: 21460441
references.citation: Acta Crystallogr D Biol Crystallogr. 2008 Jan;64(Pt 1):119-24
references.pmid: 18094475
references.citation: Hum Mol Genet. 2008 Nov 15;17(22):3521-31
references.pmid: 18725397
references.citation: Proc Natl Acad Sci U S A. 2000 Aug 1;97(16):8932-7
references.pmid: 10908679
references.citation: FEBS Lett. 1999 Jul 30;456(1):13-6
references.pmid: 10452520
references.citation: Biochemistry. 2004 Jun 1;43(21):6511-8
references.pmid: 15157084
references.citation: Proteins. 2005 May 1;59(2):221-30
references.pmid: 15726624
references.citation: FEBS J. 2007 Aug;274(16):4199-210
references.pmid: 17651435
references.citation: J Biol Chem. 2000 Oct 6;275(40):30753-6
references.pmid: 10900192
references.citation: Structure. 2004 Nov;12(11):2037-48
references.pmid: 15530368
references.citation: J Biol Chem. 1969 Jul 10;244(13):3613-7
references.pmid: 5794228
references.citation: Protein Sci. 2010 Jan;19(1):99-110
references.pmid: 19916167
references.citation: Methods Enzymol. 1997;276:307-26
references.pmid: 27754618
references.citation: J Biol Chem. 2013 Aug 23;288(34):24777-87
references.pmid: 23839945
references.citation: Acta Crystallogr D Biol Crystallogr. 2010 Feb;66(Pt 2):213-21
references.pmid: 20124702
references.citation: J Am Chem Soc. 2003 May 21;125(20):6078-84
references.pmid: 12785837
references.citation: J Fluoresc. 2010 Mar;20(2):625-9
references.pmid: 19997966
references.citation: BMC Genomics. 2008 May 06;9:210
references.pmid: 18460197
references.citation: Acta Crystallogr D Biol Crystallogr. 2011 Apr;67(Pt 4):355-67
references.pmid: 21460454
references.citation: Biochem J. 2006 Sep 15;398(3):605-11
references.pmid: 16787388
references.citation: J Mol Biol. 2007 Sep 21;372(3):774-97
references.pmid: 17681537
references.citation: Biochemistry. 2012 Mar 27;51(12):2506-14
references.pmid: 22352884
references.citation: Structure. 2000 Jul 15;8(7):695-707
references.pmid: 10903947
references.citation: Nature. 1992 Jan 30;355(6359):472-5
references.pmid: 18481394
references.citation: Nat Commun. 2010 Oct 19;1:95
references.pmid: 20981023
references.citation: Acta Crystallogr D Biol Crystallogr. 2004 Dec;60(Pt 12 Pt 1):2126-32
references.pmid: 15572765
references.citation: Biochim Biophys Acta. 2013 Jun;1834(6):1168-80
references.pmid: 23429177
references.citation: Am J Hum Genet. 2000 Sep;67(3):549-62
references.pmid: 10930361
references.citation: J Mol Biol. 2004 Aug 6;341(2):605-15
references.pmid: 15276847
references.citation: EMBO Rep. 2004 Nov;5(11):1096-101
references.pmid: 15472712
references.citation: J Inorg Biochem. 2003 Jan 1;93(1-2):66-70
references.pmid: 12538054
references.citation: J Mol Biol. 2011 Dec 16;414(5):783-97
references.pmid: 22051511
references.citation: EMBO Rep. 2007 Feb;8(2):194-9
references.pmid: 17186026
references.citation: Acta Crystallogr D Biol Crystallogr. 2012 Apr;68(Pt 4):454-67
references.pmid: 22505266