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PDBsum entry 3e2c
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Oxidoreductase
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PDB id
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3e2c
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References listed in PDB file
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Key reference
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Title
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Structural and mechanistic studies of a stabilized subunit dimer variant of escherichia coli bacterioferritin identify residues required for core formation.
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Authors
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S.G.Wong,
S.A.Tom-Yew,
A.Lewin,
N.E.Le brun,
G.R.Moore,
M.E.Murphy,
A.G.Mauk.
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Ref.
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J Biol Chem, 2009,
284,
18873-18881.
[DOI no: ]
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PubMed id
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Note In the PDB file this reference is
annotated as "TO BE PUBLISHED".
The citation details given above were identified by an automated
search of PubMed on title and author
names, giving a
perfect match.
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Abstract
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Bacterioferritin (BFR) is a bacterial member of the ferritin family that
functions in iron metabolism and protects against oxidative stress. BFR differs
from the mammalian protein in that it is comprised of 24 identical subunits and
is able to bind 12 equivalents of heme at sites located between adjacent pairs
of subunits. The mechanism by which iron enters the protein to form the
dinuclear (ferroxidase) catalytic site present in every subunit and the
mineralized iron core housed within the 24-mer is not well understood. To
address this issue, the properties of a catalytically functional assembly
variant (E128R/E135R) of Escherichia coli BFR are characterized by a combination
of X-ray crystallography, site directed mutagenesis, and kinetics. The
three-dimensional structure of the protein (1.8 A resolution) includes two
ethylene glycol molecules located on either side of the dinuclear iron site. One
of these ethylene glycol molecules is integrated into the surface of the protein
that would normally be exposed to solvent (the outer surface) and the other is
integrated into the surface of the protein that would normally face the iron
core (the inner surface) where it is surrounded by the negatively charged
residues E47, D50, and D126. We propose that the sites occupied by these
ethylene glycol molecules define regions where iron interacts with the protein,
and, in keeping with this proposal, a significant reduction in ferroxidase
activity results on replacing them with the corresponding amides.
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Figure 2.
Images of the partially occupied dinuclear iron site.A, 2F[o]
− F[c] representative electron density of the dinuclear iron
site contoured at 1 σ (blue) and 5 σ (green). B, the metal ion
(magenta) and ethylene glycol (yellow) are highlighted. His^130
is directed away from the vacant site where the iron is normally
coordinated by His^130.
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Figure 3.
Molecular surfaces showing the ferroxidase pore openings at
the inner and outer surface.A, side view showing the relative
positions of the ethylene glycol molecules and metal ion inside
the protein. B, outer surface of BFR subunit dimer showing
ethylene glycol molecule colored yellow in outer pore. C, inner
surface of wild-type BFR showing previously observed
conformations of His^46, Glu^47, and His^130 in the closed
state. D, inner surface of BFR subunit dimer showing ethylene
glycol molecule in inner pore and alternate conformations of
His^46, Glu^47, and His^130 in the open state.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2009,
284,
18873-18881)
copyright 2009.
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