2b3y

Structure of a monoclinic crystal form of human cytosolic aconitase (IRP1)Structure of a monoclinic crystal form of human cytosolic aconitase (IRP1)

Structural highlights

2b3y is a 2 chain structure with sequence from Homo sapiens. The May 2007 RCSB PDB Molecule of the Month feature on Aconitase and Iron Regulatory Protein 1 by David S. Goodsell is 10.2210/rcsb_pdb/mom_2007_5. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	X-ray diffraction, Resolution 1.85Å
Ligands:	, , ,
Resources:	FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

ACOHC_HUMAN Bifunctional iron sensor that switches between 2 activities depending on iron availability (PubMed:1946430, PubMed:1281544, PubMed:8041788). Iron deprivation, promotes its mRNA binding activity through which it regulates the expression of genes involved in iron uptake, sequestration and utilization (PubMed:1946430, PubMed:1281544, PubMed:8041788, PubMed:23891004). Binds to iron-responsive elements (IRES) in the untranslated region of target mRNAs preventing for instance the translation of ferritin and aminolevulinic acid synthase and stabilizing the transferrin receptor mRNA (PubMed:1946430, PubMed:1281544, PubMed:8041788, PubMed:23891004).^[1] ^[2] ^[3] ^[4] Conversely, when cellular iron levels are high, binds a 4Fe-4S cluster which precludes RNA binding activity and promotes the aconitase activity, the isomerization of citrate to isocitrate via cis-aconitate.^[5] ^[6] ^[7]

Evolutionary Conservation

Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.

Publication Abstract from PubMed

Iron regulatory proteins (IRPs) control the translation of proteins involved in iron uptake, storage and utilization by binding to specific noncoding sequences of the corresponding mRNAs known as iron-responsive elements (IREs). This strong interaction assures proper iron homeostasis in animal cells under iron shortage. Conversely, under iron-replete conditions, IRP1 binds a [4Fe-4S] cluster and functions as cytosolic aconitase. Regulation of the balance between the two IRP1 activities is complex, and it does not depend only on iron availability. Here, we report the crystal structure of human IRP1 in its aconitase form. Comparison with known structures of homologous enzymes reveals well-conserved folds and active site environments with significantly different surface shapes and charge distributions. The specific features of human IRP1 allow us to propose a tentative model of an IRP1-IRE complex that agrees with a range of previously obtained data.

Crystal structure of human iron regulatory protein 1 as cytosolic aconitase.,Dupuy J, Volbeda A, Carpentier P, Darnault C, Moulis JM, Fontecilla-Camps JC Structure. 2006 Jan;14(1):129-39. PMID:16407072^[8]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

↑ Haile DJ, Rouault TA, Harford JB, Kennedy MC, Blondin GA, Beinert H, Klausner RD. Cellular regulation of the iron-responsive element binding protein: disassembly of the cubane iron-sulfur cluster results in high-affinity RNA binding. Proc Natl Acad Sci U S A. 1992 Dec 15;89(24):11735-9. PMID:1281544 doi:10.1073/pnas.89.24.11735
↑ Kaptain S, Downey WE, Tang C, Philpott C, Haile D, Orloff DG, Harford JB, Rouault TA, Klausner RD. A regulated RNA binding protein also possesses aconitase activity. Proc Natl Acad Sci U S A. 1991 Nov 15;88(22):10109-13. PMID:1946430
↑ Stehling O, Mascarenhas J, Vashisht AA, Sheftel AD, Niggemeyer B, Rösser R, Pierik AJ, Wohlschlegel JA, Lill R. Human CIA2A-FAM96A and CIA2B-FAM96B integrate iron homeostasis and maturation of different subsets of cytosolic-nuclear iron-sulfur proteins. Cell Metab. 2013 Aug 6;18(2):187-98. PMID:23891004 doi:10.1016/j.cmet.2013.06.015
↑ Philpott CC, Klausner RD, Rouault TA. The bifunctional iron-responsive element binding protein/cytosolic aconitase: the role of active-site residues in ligand binding and regulation. Proc Natl Acad Sci U S A. 1994 Jul 19;91(15):7321-5. PMID:8041788
↑ Haile DJ, Rouault TA, Harford JB, Kennedy MC, Blondin GA, Beinert H, Klausner RD. Cellular regulation of the iron-responsive element binding protein: disassembly of the cubane iron-sulfur cluster results in high-affinity RNA binding. Proc Natl Acad Sci U S A. 1992 Dec 15;89(24):11735-9. PMID:1281544 doi:10.1073/pnas.89.24.11735
↑ Kaptain S, Downey WE, Tang C, Philpott C, Haile D, Orloff DG, Harford JB, Rouault TA, Klausner RD. A regulated RNA binding protein also possesses aconitase activity. Proc Natl Acad Sci U S A. 1991 Nov 15;88(22):10109-13. PMID:1946430
↑ Philpott CC, Klausner RD, Rouault TA. The bifunctional iron-responsive element binding protein/cytosolic aconitase: the role of active-site residues in ligand binding and regulation. Proc Natl Acad Sci U S A. 1994 Jul 19;91(15):7321-5. PMID:8041788
↑ Dupuy J, Volbeda A, Carpentier P, Darnault C, Moulis JM, Fontecilla-Camps JC. Crystal structure of human iron regulatory protein 1 as cytosolic aconitase. Structure. 2006 Jan;14(1):129-39. PMID:16407072 doi:10.1016/j.str.2005.09.009

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OCA

[1] Haile DJ, Rouault TA, Harford JB, Kennedy MC, Blondin GA, Beinert H, Klausner RD. Cellular regulation of the iron-responsive element binding protein: disassembly of the cubane iron-sulfur cluster results in high-affinity RNA binding. Proc Natl Acad Sci U S A. 1992 Dec 15;89(24):11735-9. PMID:1281544 doi:10.1073/pnas.89.24.11735

[2] Kaptain S, Downey WE, Tang C, Philpott C, Haile D, Orloff DG, Harford JB, Rouault TA, Klausner RD. A regulated RNA binding protein also possesses aconitase activity. Proc Natl Acad Sci U S A. 1991 Nov 15;88(22):10109-13. PMID:1946430

[3] Stehling O, Mascarenhas J, Vashisht AA, Sheftel AD, Niggemeyer B, Rösser R, Pierik AJ, Wohlschlegel JA, Lill R. Human CIA2A-FAM96A and CIA2B-FAM96B integrate iron homeostasis and maturation of different subsets of cytosolic-nuclear iron-sulfur proteins. Cell Metab. 2013 Aug 6;18(2):187-98. PMID:23891004 doi:10.1016/j.cmet.2013.06.015

[4] Philpott CC, Klausner RD, Rouault TA. The bifunctional iron-responsive element binding protein/cytosolic aconitase: the role of active-site residues in ligand binding and regulation. Proc Natl Acad Sci U S A. 1994 Jul 19;91(15):7321-5. PMID:8041788

[5] Haile DJ, Rouault TA, Harford JB, Kennedy MC, Blondin GA, Beinert H, Klausner RD. Cellular regulation of the iron-responsive element binding protein: disassembly of the cubane iron-sulfur cluster results in high-affinity RNA binding. Proc Natl Acad Sci U S A. 1992 Dec 15;89(24):11735-9. PMID:1281544 doi:10.1073/pnas.89.24.11735

[6] Kaptain S, Downey WE, Tang C, Philpott C, Haile D, Orloff DG, Harford JB, Rouault TA, Klausner RD. A regulated RNA binding protein also possesses aconitase activity. Proc Natl Acad Sci U S A. 1991 Nov 15;88(22):10109-13. PMID:1946430

[7] Philpott CC, Klausner RD, Rouault TA. The bifunctional iron-responsive element binding protein/cytosolic aconitase: the role of active-site residues in ligand binding and regulation. Proc Natl Acad Sci U S A. 1994 Jul 19;91(15):7321-5. PMID:8041788

[8] Dupuy J, Volbeda A, Carpentier P, Darnault C, Moulis JM, Fontecilla-Camps JC. Crystal structure of human iron regulatory protein 1 as cytosolic aconitase. Structure. 2006 Jan;14(1):129-39. PMID:16407072 doi:10.1016/j.str.2005.09.009

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