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PDBsum entry 1j3y
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Oxygen storage/transport
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PDB id
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1j3y
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Direct observation of photolysis-Induced tertiary structural changes in hemoglobin.
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Authors
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S.Adachi,
S.Y.Park,
J.R.Tame,
Y.Shiro,
N.Shibayama.
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Ref.
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Proc Natl Acad Sci U S A, 2003,
100,
7039-7044.
[DOI no: ]
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PubMed id
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Abstract
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Human Hb, an alpha2beta2 tetrameric oxygen transport protein that switches from
a T (tense) to an R (relaxed) quaternary structure during oxygenation, has long
served as a model for studying protein allostery in general. Time-resolved
spectroscopic measurements after photodissociation of CO-liganded Hb have played
a central role in exploring both protein dynamical responses and molecular
cooperativity, but the direct visualization and the structural consequences of
photodeligation have not yet been reported. Here we present an x-ray study of
structural changes induced by photodissociation of half-liganded T-state and
fully liganded R-state human Hb at cryogenic temperatures (25-35 K). On
photodissociation of CO, structural changes involving the heme and the F-helix
are more marked in the alpha subunit than in the beta subunit, and more subtle
in the R state than in the T state. Photodeligation causes a significant sliding
motion of the T-state beta heme. Our results establish that the structural basis
of the low affinity of the T state is radically different between the subunits,
because of differences in the packing and chemical tension at the hemes.
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Figure 1.
Fig. 1. Stereoview of electron density maps (2F[o] - F[c]
map) of the active-site structures of photolysed CO complexes of
T-state hybrid Hbs contoured at 1.3  . (a) The  1 heme
region in photolysed XL[ (Fe-CO)  (Ni)][2]
(molecule 1) at 25 K. (b) The 2 heme region in
photolysed XL[ (Ni) (Fe-CO)][2] (molecule 2)
at 25 K.
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Figure 3.
Fig. 3. Stereoview of difference Fourier maps of the
active-site structures between the R-state photoproduct and the
CO-bound structure contoured at ±3 . (a) The heme
region in HbCO at 35 K. (b) The heme region in HbCO at
35 K.
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