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Site-directed Replacement of the Coaxial Heme Ligands of Bacterioferritin Generates Heme-free Variants
Site-directed Replacement of the Coaxial Heme Ligands of Bacterioferritin Generates Heme-free Variants
- Source :
- Journal of Biological Chemistry. 270:23268-23274
- Publication Year :
- 1995
- Publisher :
- Elsevier BV, 1995.
-
Abstract
- The bacterioferritin (BFR) of Escherichia coli is a heme-containing iron storage molecule. It is composed of 24 identical subunits, which form a roughly spherical protein shell surrounding a central iron storage cavity. Each of the 12 heme moieties of BFR possesses bis-methionine axial ligation, a heme coordination scheme so far only found in bacterioferritins. Members of the BFR family contain three partially conserved methionine residues (excluding the initiating methionine) and in this study each was substituted by leucine and/or histidine. The Met52 variants were devoid of heme, whereas the Met31 and Met86 variants possessed full heme complements and were spectroscopically indistinguishable from wild-type BFR. The heme-free Met52 variants appeared to be correctly assembled and were capable of accumulating iron both in vivo and in vitro. No major differences were observed in the overall rate of iron accumulation for BFR-M52H, BFR-M52L, and the wild-type protein. The iron contents of the Met52 variants, as isolated, were at least 4 times greater than for wild-type BFR. This study is consistent with the reported location of the BFR heme site at the 2-fold axis and shows that heme is unnecessary for BFR assembly and iron uptake.
- Subjects :
- Stereochemistry
Iron
Molecular Sequence Data
Heme
Ligands
medicine.disease_cause
Biochemistry
chemistry.chemical_compound
Bacterial Proteins
Escherichia coli
medicine
Amino Acid Sequence
Molecular Biology
Histidine
DNA Primers
Iron uptake
Binding Sites
Methionine
Base Sequence
biology
Electron Spin Resonance Spectroscopy
Genetic Variation
Cell Biology
Bacterioferritin
Cytochrome b Group
In vitro
chemistry
Genes, Bacterial
Spectrophotometry
Ferritins
Mutagenesis, Site-Directed
biology.protein
Leucine
Oxidation-Reduction
Subjects
Details
- ISSN :
- 00219258
- Volume :
- 270
- Database :
- OpenAIRE
- Journal :
- Journal of Biological Chemistry
- Accession number :
- edsair.doi.dedup.....fe9976efeacb136696abef2ecb327974
- Full Text :
- https://doi.org/10.1074/jbc.270.40.23268