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PDBsum entry 1bab
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Oxygen transport
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PDB id
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1bab
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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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Hemoglobin thionville. An alpha-Chain variant with a substitution of a glutamate for valine at na-1 and having an acetylated methionine nh2 terminus.
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Authors
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C.Vasseur,
Y.Blouquit,
J.Kister,
D.Promé,
J.S.Kavanaugh,
P.H.Rogers,
C.Guillemin,
A.Arnone,
F.Galacteros,
C.Poyart.
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Ref.
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J Biol Chem, 1992,
267,
12682-12691.
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PubMed id
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Abstract
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In hemoglobin (Hb) Thionville, the substitution of a glutamic acid for the
alpha-chain NH2-terminal valine inhibits the cleavage of the initiator
methionine which is then acetylated. The elongation of the alpha-chain NH2
terminus modifies the three-dimensional structure of hemoglobin at a region that
is known to have an important role in the allosteric regulation of oxygen
binding. Relative to Hb A, Hb Thionville has a lower affinity for oxygen, and
the heterotropic allosteric effects of protons, chloride, and bezafibrate are
reduced. In contrast, the response to 2,3-diphosphoglycerate is normal. Analysis
of oxygen equilibrium data within the framework of the two-state allosteric
model indicates that the structure of deoxy Hb Thionville is stabilized relative
to that of deoxy Hb A. The x-ray crystal structure of deoxy Hb Thionville shows
that the glutamate side chain extends away from the alpha 1-alpha 2 interface,
whereas the methionine side chain (which has two conformations) extends into the
alpha 1-alpha 2 interface, physically displacing chloride and bezafibrate. The
increased stability of deoxy Hb Thionville is due to new intrasubunit and
intersubunit contacts made by the methionine. These interactions replace the
indirect contacts, made through bound chloride ions, that Val-1 alpha normally
contributes to the alpha 1-alpha 2 interface.
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