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Title
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Binding mode of azide to ferric Aplysia limacina myoglobin. Crystallographic analysis at 1.9 A resolution.
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Authors
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A.Mattevi,
G.Gatti,
A.Coda,
M.Rizzi,
P.Ascenzi,
M.Brunori,
M.Bolognesi.
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Ref.
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J Mol Recognit, 1991,
4,
1-6.
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PubMed id
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Abstract
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The binding mode of azide to the ferric form of Aplysia limacina myoglobin has
been studied by X-ray crystallography. The three-dimensional structure of the
complex has been refined at 1.9 A resolution to a crystallographic R-factor of
13.9%, including 126 ordered solvent molecules. Azide binds to the heme iron, at
the sixth co-ordination position, and is oriented towards the outer part of the
distal site crevice. This orientation is stabilized by an ionic interaction with
the side-chain of Arg66 (E10) which, from an outer orientation in the 'aquo-met'
ligand-free myoglobin, folds back towards the distal site in the presence of the
anionic ligand. In the absence of a hydrogen bond donor residue at the distal E7
position in Aplysia limacina myoglobin, a different polar residue, Arg66 at the
E10 topological position, has been selected by molecular evolution in order to
grant ligand stabilization.
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