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PDBsum entry 1it2
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Oxygen storage/transport
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PDB id
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1it2
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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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Crystal structures of deoxy- And carbonmonoxyhemoglobin f1 from the hagfish eptatretus burgeri.
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Authors
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M.Mito,
K.T.Chong,
G.Miyazaki,
S.Adachi,
S.Y.Park,
J.R.Tame,
H.Morimoto.
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Ref.
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J Biol Chem, 2002,
277,
21898-21905.
[DOI no: ]
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PubMed id
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Abstract
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Hagfish are extremely primitive jawless fish of disputed ancestry. Although
generally classed with lampreys as cyclostomes ("round mouths"), it is
clear that they diverged from them several hundred million years ago. The
crystal structures of the deoxy and CO forms of hemoglobin from a hagfish
(Eptatretus burgeri) have been solved at 1.6 and 2.1 A, respectively. The deoxy
crystal contains one dimer and two monomers in a unit cell, with the dimer being
similar to that found in lamprey deoxy-Hb, but with a larger interface and
different relative orientation of the partner chains. Ile(E11) and Gln(E7)
obstruct ligand binding in the deoxy form and make room for ligands in the CO
form, but no interaction path between the two hemes could be identified. The BGH
core structure, which forms the alpha1beta1 interface of all vertebrate
alpha2beta2 tetrameric Hbs, is conserved in hagfish and lamprey Hbs. It was
shown previously that human and cartilaginous fish Hbs have independently
evolved stereochemical mechanisms other than the movement of the proximal
histidine to regulate ligand binding at the hemes. Our results therefore suggest
that the formation of the alpha2beta2 tetramer using the BGH core and the
mechanism of quaternary structure change evolved between the branching points of
hagfish and lampreys from other vertebrates.
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Figure 3.
Fig. 3. Comparison of the E. burgeri deoxy-Hb F1 dimer
(A) with the lamprey Hb V dimer (B) (Protein Data Bank code
3lhb). The E and F helices and AB corners are indicated. Lamprey
deoxy-Hb has a more open conformation in the upper half of the
interface, and the F helices do not contribute to dimer
formation.
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Figure 6.
Fig. 6. 2F[o]  F[c]
electron density map showing the heme of deoxy-Hb F1. The map is
contoured at 1.3  and clearly
shows the absence of ligand bound to the heme. The resolution of
the data is high enough to model the side chain conformations of
residues around the heme unambiguously.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2002,
277,
21898-21905)
copyright 2002.
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