Dataset Information

The iron-responsive element-binding protein: localization of the RNA-binding site to the aconitase active-site cleft.

ABSTRACT: The iron-responsive element-binding protein (IRE-BP) binds to specific stem-loop RNA structures known as iron-responsive elements (IREs) present in a variety of cellular mRNAs (e.g., those encoding ferritin, erythroid 5-aminolevulinate synthase, and transferrin receptor). Expression of these genes is regulated by interaction with the IRE-BP. The IRE-BP is identical in sequence to cytosolic aconitase, and the function of the protein is determined by the presence or absence of an Fe-S cluster. The protein either functions as an active aconitase when the Fe-S cluster is present or as an RNA-binding protein when the protein lacks this cluster. Aconitase activity and IRE-binding activity are mutually exclusive, and interconversion between the two activities is determined by intracellular Fe concentrations. Mapping of the RNA-binding site of the IRE-BP by UV cross-linking studies defines a major contact site between IRE and protein in the active-site region. Modeling based on probable structural similarities between the previously crystallized mitochondrial aconitase and the IRE-BP predicts that these residues would be accessible to the IRE only were there a major change in the predicted conformation of the protein when cells are iron-depleted.

SUBMITTER: Basilion JP

PROVIDER: S-EPMC42991 | biostudies-other | 1994 Jan

REPOSITORIES: biostudies-other

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Publications

The iron-responsive element-binding protein: localization of the RNA-binding site to the aconitase active-site cleft.

Basilion J P JP Rouault T A TA Massinople C M CM Klausner R D RD Burgess W H WH

Proceedings of the National Academy of Sciences of the United States of America 19940101 2

The iron-responsive element-binding protein (IRE-BP) binds to specific stem-loop RNA structures known as iron-responsive elements (IREs) present in a variety of cellular mRNAs (e.g., those encoding ferritin, erythroid 5-aminolevulinate synthase, and transferrin receptor). Expression of these genes is regulated by interaction with the IRE-BP. The IRE-BP is identical in sequence to cytosolic aconitase, and the function of the protein is determined by the presence or absence of an Fe-S cluster. The ...[more]

PMID: 8290565

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Project description:Legionella pneumophila has high iron requirements, and its intracellular growth in human monocytes is dependent on the availability of intracellular iron. To learn more about iron metabolism in L. pneumophila, we have undertaken an analysis of the iron proteins of the bacterium. We first developed an assay to identify proteins by 59Fe labelling and nondenaturing polyacrylamide gel electrophoresis. The assay revealed seven iron proteins (IPs) with apparent molecular weights of 500, 450, 250, 210, 150, 130, and 85. IP150 comigrates with superoxide dismutase activity and is probably the Fe-superoxide dismutase of L. pneumophila. IP210 is the major iron-containing protein (MICP). To identify and characterize MICP, we purified the protein and cloned and sequenced its gene. MICP is a monomeric protein containing 891 amino acids, and it has a calculated molecular mass of 98,147 Da. Analysis of the sequence revealed that MICP has two interesting homologies. First, MICP is highly homologous with the human iron-responsive element-binding protein, consistent with the hypothesis that this critical iron-regulatory molecule of humans has a prokaryotic ancestor. Second, MICP is highly homologous with the Escherichia coli aconitase and to a lesser extent with porcine heart mitochondrial aconitase. Consistent with this, we found that MICP exhibits aconitase activity. In contrast to other aconitases, MICP has a single amino acid change of a potentially deleterious type at a site thought to be critical for substrate binding and enzymatic activity. However, the specific activity of MICP is roughly comparable to that of other aconitases, suggesting that the mutation has at most a mild effect on the aconitase activity of MICP. The abundance of MICP in L. pneumophila suggests either that L. pneumophila requires high aconitase and perhaps tricarboxylic acid cycle activity or that the bacterium requires large amounts of this protein to serve an additional role in bacterial physiology. A need for large amounts of MICP, which contains four Fe atoms per molecule when fully loaded, could at least partly explain L. pneumophila's high metabolic requirement for iron.

Dataset Information

The iron-responsive element-binding protein: localization of the RNA-binding site to the aconitase active-site cleft.

Publications

The iron-responsive element-binding protein: localization of the RNA-binding site to the aconitase active-site cleft.

Similar Datasets

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