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PDBsum entry 1k1k
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Oxygen storage/transport
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PDB id
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1k1k
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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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Structure of mutant human carbonmonoxyhemoglobin c (betae6k) at 2.0 a resolution.
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Authors
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J.C.Dewan,
A.Feeling-Taylor,
Y.A.Puius,
L.Patskovska,
Y.Patskovsky,
R.L.Nagel,
S.C.Almo,
R.E.Hirsch.
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Ref.
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Acta Crystallogr D Biol Crystallogr, 2002,
58,
2038-2042.
[DOI no: ]
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PubMed id
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Abstract
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Previous studies have demonstrated that in vitro crystallization of R-state
liganded hemoglobin C (HbC), a naturally occurring mutant human hemoglobin
(betaE6K), in high-phosphate buffer solutions provides a potential model system
for the intracellular crystallization of HbC associated with chronic hemolytic
anemia in CC disease. The first high-resolution crystal structure of liganded
HbC is reported here. HbC was crystallized from high phosphate and the structure
of the carbonmonoxy-liganded R-state form was refined at 2.0 A resolution.
Crystals exhibit diffraction consistent with the tetragonal space group
P4(1)2(1)2, with unit-cell parameters a = 54.16, c = 195.30 A. The structure was
solved by difference Fourier techniques and refinement by simulated annealing
and restrained least-squares yielded a final R of 0.183 and an R(free) of 0.238
for all 19,382 unique reflections. The side chain of betaK6 exhibits very weak
electron density consistent with significant mobility within the crystalline
lattice. The highly dynamic nature of the side chain could potentially support a
number of specific polar interactions that might reduce the barrier to
crystallization and thus result in enhanced crystallization kinetics for HbC
relative to HbA. Specifically, the NZ atom of the BK6 side chain could
participate in an amino-aromatic hydrogen bond with the pi-electron cloud of
betaH116 in a symmetry-related tetramer. BetaK6 NZ might also interact with the
main-chain carbonyl O atom of betaH117 and the carboxylate group of betaE22 from
a symmetry-related tetramer.
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Figure 2.
Figure 2 Electron-density map of the  -chain
heme pocket of the 2  resolution
of COHbC showing the high quality of the electron-density map,
as exemplified by the proximal and distal histidines, and the
heme group and CO molecule. Stereoview of 2F[o] - F[c]
electron-density contour map built around the heme, His58 and
His87 of the -subunit
of COHbC.
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The above figure is
reprinted
by permission from the IUCr:
Acta Crystallogr D Biol Crystallogr
(2002,
58,
2038-2042)
copyright 2002.
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