scholarly journals Accommodating variety in iron-responsive elements: Crystal structure of transferrin receptor 1 B IRE bound to iron regulatory protein 1

FEBS Letters ◽  
2011 ◽  
Vol 586 (1) ◽  
pp. 32-35 ◽  
Author(s):  
William E. Walden ◽  
Anna Selezneva ◽  
Karl Volz
Keyword(s):  
Crystal Structure ◽  
Transferrin Receptor ◽  
Regulatory Protein ◽  
Iron Regulatory Protein ◽  
Transferrin Receptor 1 ◽  
Iron Responsive Elements ◽  
Iron Regulatory Protein 1

scholarly journals Crystal Structure of Human Iron Regulatory Protein 1 as Cytosolic Aconitase

Structure ◽  
2006 ◽  
Vol 14 (1) ◽  
pp. 129-139 ◽  
Author(s):  
Jérôme Dupuy ◽  
Anne Volbeda ◽  
Philippe Carpentier ◽  
Claudine Darnault ◽  
Jean-Marc Moulis ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Regulatory Protein ◽  
Iron Regulatory Protein ◽  
Iron Regulatory Protein 1

scholarly journals Cysteine Oxidation Regulates the RNA-Binding Activity of Iron Regulatory Protein 2

2009 ◽  
Vol 29 (8) ◽  
pp. 2219-2229 ◽  
Author(s):  
Kimberly B. Zumbrennen ◽  
Michelle L. Wallander ◽  
S. Joshua Romney ◽  
Elizabeth A. Leibold
Keyword(s):  
Oxidative Stress ◽  
Transferrin Receptor ◽  
Iron Homeostasis ◽  
Rna Binding ◽  
Regulatory Protein ◽  
Binding Activity ◽  
Structural Basis ◽  
Iron Regulatory Protein ◽  
Transferrin Receptor 1 ◽  
Binding Cleft

ABSTRACT Iron regulatory protein 2 (IRP2) is an RNA-binding protein that regulates the posttranscriptional expression of proteins required for iron homeostasis such as ferritin and transferrin receptor 1. IRP2 RNA-binding activity is primarily regulated by iron-mediated proteasomal degradation, but studies have suggested that IRP2 RNA binding is also regulated by thiol oxidation. We generated a model of IRP2 bound to RNA and found that two cysteines (C512 and C516) are predicted to lie in the RNA-binding cleft. Site-directed mutagenesis and thiol modification show that, while IRP2 C512 and C516 do not directly interact with RNA, both cysteines are located within the RNA-binding cleft and must be unmodified/reduced for IRP2-RNA interactions. Oxidative stress induced by cellular glucose deprivation reduces the RNA-binding activity of IRP2 but not IRP2-C512S or IRP2-C516S, consistent with the formation of a disulfide bond between IRP2 C512 and C516 during oxidative stress. Decreased IRP2 RNA binding is correlated with reduced transferrin receptor 1 mRNA abundance. These studies provide insight into the structural basis for IRP2-RNA interactions and reveal an iron-independent mechanism for regulating iron homeostasis through the redox regulation of IRP2 cysteines.

scholarly journals A Phosphomimetic Mutation at Ser-138 Renders Iron Regulatory Protein 1 Sensitive to Iron-Dependent Degradation

2003 ◽  
Vol 23 (19) ◽  
pp. 6973-6981 ◽  
Author(s):  
Carine Fillebeen ◽  
Danielle Chahine ◽  
Annie Caltagirone ◽  
Phillip Segal ◽  
Kostas Pantopoulos
Keyword(s):  
Mammalian Cells ◽  
Regulatory Protein ◽  
Proteasome Inhibitors ◽  
Iron Chelator ◽  
Binding Activity ◽  
Iron Regulatory Protein ◽  
Cluster Assembly ◽  
The Stability ◽  
Iron Responsive Elements ◽  
Iron Regulatory Protein 1

ABSTRACT Iron regulatory protein 1 (IRP1) binds to mRNA iron-responsive elements (IREs) and thereby controls the expression of IRE-containing mRNAs. In iron-replete cells, assembly of a cubane [4Fe-4S] cluster inhibits IRE-binding activity and converts IRP1 to a cytosolic aconitase. Earlier experiments with Saccharomyces cerevisiae suggested that phosphomimetic mutations of Ser-138 negatively affect the stability of the cluster (N. M. Brown, S. A. Anderson, D. W. Steffen, T. B. Carpenter, M. C. Kennedy, W. E. Walden, and R. S. Eisenstein, Proc. Natl. Acad. Sci. USA 95:15235-15240, 1998). Along these lines, we show here that a highly purified preparation of recombinant human IRP1 bearing a phosphomimetic S138E substitution (IRP1S138E) lacks aconitase activity, which is a hallmark of [4Fe-4S] cluster integrity. Similarly, IRP1S138E expressed in mammalian cells fails to function as aconitase. Furthermore, we demonstrate that the impairment of [4Fe-4S] cluster assembly in mammalian cells sensitizes IRP1S138E to iron-dependent degradation. This effect can be completely blocked by the iron chelator desferrioxamine or by the proteasome inhibitors MG132 and lactacystin. As expected, the stability of wild-type or phosphorylation-deficient IRP1S138A is not affected by iron manipulations. Ser-138 and flanking sequences appear to be highly conserved in the IRP1s of vertebrates, whereas insect IRP1 orthologues and nonvertebrate IRP1-like molecules contain an S138A substitution. Our data suggest that phosphorylation of Ser-138 may provide a basis for an additional mechanism for the control of vertebrate IRP1 activity at the level of protein stability.

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