Spectroscopic and voltammetric characterisation of the bacterioferritin-associated ferredoxin of Escherichia coli.
The bacterioferritin-associated ferredoxin (Bfd) of Escherichia coli is a 64-residue polypeptide encoded by the bfd gene located upstream of the gene (bfr) encoding the iron-storage haemoprotein, bacterioferritin. The Bfd sequence resembles those of the approximately 60-residue domains found in NifU proteins (required for metallocluster assembly), nitrite reductases, and Klebsiella pneumoniae nitrate reductase. These related-domains contain four well-conserved cysteine residues, which are thought to function as ligands to a [2Fe-2S] cluster. The Bfd protein was over-produced, purified, and characterised. Bfd was found to be a positively-charged monomer containing two iron atoms and two labile sulphides. Ultraviolet-visible, EPR, variable-temperature magnetic-circular dichroism and resonance Raman spectroscopies, together with cyclic voltogram measurements, revealed the presence of a [2Fe-2S]2+,+ centre (E1/2 = -254 mV) having remarkably similar properties to the Fe-S cluster of NifU. Bfd may thus be a 2Fe ferredoxin participating either in release/delivery of iron from/to bacterioferritin (or other iron complexes), or in iron-dependent regulation of bfr expression.
Quail
M A
MA
Krebs Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, United Kingdom.
Jordan
P
P
Grogan
J M
JM
Butt
J N
JN
Lutz
M
M
Thomson
A J
AJ
Andrews
S C
SC
Guest
J R
JR
D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D003573:Cytochrome b Group / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D004563:Electrochemistry; D004926:Escherichia coli / Q000737:chemistry*; D005288:Ferredoxins / Q000737:chemistry*; D005293:Ferritins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D005982:Glutathione Transferase / Q000235:genetics; D008969:Molecular Sequence Data; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D013057:Spectrum Analysis
D001426:Bacterial Proteins; D003573:Cytochrome b Group; D005288:Ferredoxins; D011993:Recombinant Fusion Proteins; D005293:Ferritins; C018032:bacterioferritin; D005982:Glutathione Transferase