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PDBsum entry 2v1h
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Oxygen transport
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PDB id
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2v1h
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References listed in PDB file
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Key reference
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Title
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Crystallographic and spectroscopic studies of peroxide-Derived myoglobin compound ii and occurrence of protonated feiv o.
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Authors
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H.P.Hersleth,
T.Uchida,
A.K.Røhr,
T.Teschner,
V.Schünemann,
T.Kitagawa,
A.X.Trautwein,
C.H.Görbitz,
K.K.Andersson.
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Ref.
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J Biol Chem, 2007,
282,
23372-23386.
[DOI no: ]
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PubMed id
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Abstract
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High resolution crystal structures of myoglobin in the pH range 5.2-8.7 have
been used as models for the peroxide-derived compound II intermediates in heme
peroxidases and oxygenases. The observed Fe-O bond length (1.86-1.90 A) is
consistent with that of a single bond. The compound II state of myoglobin in
crystals was controlled by single-crystal microspectrophotometry before and
after synchrotron data collection. We observe some radiation-induced changes in
both compound II (resulting in intermediate H) and in the resting ferric state
of myoglobin. These radiation-induced states are quite unstable, and compound II
and ferric myoglobin are immediately regenerated through a short heating above
the glass transition temperature (<1 s) of the crystals. It is unclear how
this influences our compound II structures compared with the unaffected compound
II, but some crystallographic data suggest that the influence on the Fe-O bond
distance is minimal. Based on our crystallographic and spectroscopic data we
suggest that for myoglobin the compound II intermediate consists of an Fe(IV)-O
species with a single bond. The presence of Fe(IV) is indicated by a small
isomer shift of delta = 0.07 mm/s from Mössbauer spectroscopy. Earlier quantum
refinements (crystallographic refinement where the molecular-mechanics potential
is replaced by a quantum chemical calculation) and density functional theory
calculations suggest that this intermediate H species is protonated.
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Figure 5.
FIGURE 5. Crystal structures of the heme region. Structures
for radiation-induced Mb compound II (resolutions of 1.35, 1.30,
and 1.20 Å, respectively) at pH 5.2, 6.8, and 8.7,
radiation-induced ferric Mb (resolutions of 1.30, 1.20, and 1.40
Å, respectively) at pH 5.2, 6.8, and 8.7, and ferrous
deoxyMb (resolution of 1.25 Å) are shown with the electron
density 2F[o] - F[c] map (contoured at 1  in gold), the final
F[o] - F[c] map (contoured at +3 in green and at -3 in red),
and electron density difference F[o] - F[c] maps with the
iron-ligated oxygen atom (or water above the heme ring in
deoxyMb) omitted for map calculation (contoured at 5 in
magenta for the iron-ligated oxygen atom and at 4.5 for the
water in deoxyMb).
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Figure 6.
FIGURE 6. Crystal structures of the heme region of the
radiation-induced Mb compound II crystal structure at pH 5. 2
(red), 6.8 (green), and 8.7 (blue) compared with each other and
to the radiation-induced ferric Mb structures (pale colors). The
Fe–O distances, the iron to proximal His distances, the iron
to distal His distances, and the hydrogen bond distances between
the oxygen atom and the distal His are shown.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2007,
282,
23372-23386)
copyright 2007.
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