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Kinetic Analysis of Iron Responsive Element (IRE) mRNA with Iron Regulatory Protein (IRP1)
Author(s) -
KHAN MATEEN A,
Walden William E,
Theil Elizabeth C,
Goss Dixie J
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.499.7
Subject(s) - chemistry , messenger rna , rna , ferritin , biophysics , aconitase , rna binding protein , microbiology and biotechnology , biochemistry , mitochondrion , biology , gene
In mRNA a family of 5′‐noncoding structures, iron response elements (IRE), control mRNA translation. When iron concentrations decrease, IRP protein binds to the IRE‐RNA and inhibits formation of polysomes. To gain insight into the dynamic process of IRE‐mRNA/IRP regulation and the mechanism of binding, the kinetics of IRE mRNA binding to IRP1 protein were examined. The association rate constant for Ferritin IRE‐RNA was about 6‐fold faster as compared to mitochondrial IRE‐RNA (k on = 400 μM −1 s −1 for Fer‐IRE and k on = 50 μM −1 s −1 for mt‐IRE). However, the dissociation rate constant was similar for the two IRE‐RNAs binding to IRP1 protein. Addition of 50 μM magnesium ions (a model for air sensitive Fe 2+ ) decreased the rate of association 5‐fold and increased the rate of dissociation 3‐fold for Ferritin IRE‐RNA and for mitochondrial IRE‐RNA the rate of association decreased <3‐fold and the rate of dissociation increased ~2‐fold. Metal ion selective destabilization of Ferritin and mitochondrial aconitase RNA/protein complexes as reported here explain in part quantitative differences in signal response to iron in vivo and indicate possible new regulatory interactions. These results demonstrate the first direct kinetic measurements of IRP1 protein binding to IRE‐RNA. NSF: MCB‐ 0814051 (to, D.J.G.) NIH: DK20251 (to E.C.T.)