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PDBsum entry 3pal
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Calcium binding protein
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PDB id
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3pal
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References listed in PDB file
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Key reference
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Title
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Ionic interactions with parvalbumins. Crystal structure determination of pike 4.10 parvalbumin in four different ionic environments.
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Authors
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J.P.Declercq,
B.Tinant,
J.Parello,
J.Rambaud.
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Ref.
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J Mol Biol, 1991,
220,
1017-1039.
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PubMed id
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Abstract
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The crystal structure of the Ca-loaded form of pike 4.10 parvalbumin (minor
component from pike muscle belonging to the beta phylogenetic series), with both
its primary sites CD and EF occupied by Ca2+ ions and its third site occupied by
an ammonium ion, as previously determined at 1.93 A resolution, has now been
refined to a resolution of 1.65 A. The crystallization of this parvalbumin in
different ionic environments has allowed three novel non-isomorphous crystalline
forms to be obtained: (1) a first form, crystallized in the presence of a
mixture of ammonium sulphate and manganese sulphate, for which all the cation
binding sites in the protein are occupied by Mn2+; (2) a second form
crystallized in the presence of MgSO4 as the precipitating agent, only differs
from the Ca/NH4 form by the occupation of the third site by Mg2+, whereas the
primary sites remain occupied by Ca2+; (3) a third form, also crystallized in
the presence of MgSO4, corresponds to a well-defined molecular species with both
the primary EF site and the third site occupied by Mg2+, whereas the primary CD
site remains occupied by CA2+. The corresponding molecular structures reported
here have been determined at resolutions between 1.8 and 2.4 A. The comparison
of the different crystal structures allows the structural modifications
accompanying the substitution of the primary sites by cations differing
significantly in their ionic radii (Ca2+, Mn2+, Mg2+) to be investigated in
detail, and it also leads to a precise description of the third site in a
typical beta parvalbumin. The substitution Ca2+ by Mg2+ within the primary site
EF is characterized by a "contraction" of the co-ordination sphere, with a
decrease of the mean oxygen-metal distance by a value of 0.25 A and a decrease
of the co-ordination number from 7 to 6, as a consequence of the loss of a
bidentate ligand (Glu101), which becomes a monodentate one. Such an adaptation
of the co-ordination sphere around a cation of smaller size involves, among
others, the transformation of the Glu101 side-chain from the stable gauche(+)
form to the less stable gauche(-) form. The third site is clearly described as a
satellite of the CD primary site, since both sites possess common protein
ligands, such as Asp53 and Glu59. Furthermore, Asp61 appears as a specific
ligand of the third site in the different environments investigated in this
work. We finally discuss the relevance of the third site to parvalbumin
phylogeny.
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Secondary reference #1
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Title
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Crystal structure determination and refinement of pike 4.10 parvalbumin (minor component from esox lucius).
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Authors
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J.P.Declercq,
B.Tinant,
J.Parello,
G.Etienne,
R.Huber.
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Ref.
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J Mol Biol, 1988,
202,
349-353.
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PubMed id
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