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PDBsum entry 1qku
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Nuclear receptor
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PDB id
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1qku
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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 structure of a mutant heralpha ligand-Binding domain reveals key structural features for the mechanism of partial agonism.
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Authors
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M.Gangloff,
M.Ruff,
S.Eiler,
S.Duclaud,
J.M.Wurtz,
D.Moras.
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Ref.
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J Biol Chem, 2001,
276,
15059-15065.
[DOI no: ]
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PubMed id
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Abstract
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The crystal structure of a triple cysteine to serine mutant ERalpha
ligand-binding domain (LBD), complexed with estradiol, shows that despite the
presence of a tightly bound agonist ligand, the protein exhibits an
antagonist-like conformation, similar to that observed in raloxifen and
4-hydroxytamoxifen-bound structures. This mutated receptor binds estradiol with
wild type affinity and displays transcriptional activity upon estradiol
stimulation, but with limited potency (about 50%). This partial activity is
efficiently repressed in antagonist competition assays. The comparison with
available LBD structures reveals key features governing the positioning of helix
H12 and highlights the importance of cysteine residues in promoting an active
conformation. Furthermore the present study reveals a hydrogen bond network
connecting ligand binding to protein trans conformation. These observations
support a dynamic view of H12 positioning, where the control of the equilibrium
between two stable locations determines the partial agonist character of a given
ligand.
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Figure 3.
Fig. 3. Superposition of binding pockets of the wild type
(yellow) and mutant (gray) structures. The estradiol A ring
superposes perfectly in both structures, whereas the D-ring is
slightly shifted.
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Figure 5.
Fig. 5. a, effect of C417S mutation on H3. Superposition
of wild type (yellow) and Cys  Ser triple
mutant (gray) emphasizing the shortening of H3 by one turn and
the significant conformational change of the loop 1-3 are shown.
b, effect of C530S mutation on H11. Superposition of wild type
(yellow) and Cys Ser triple
mutant (gray), showing the shortening of H11 on the mutant
protein is shown. c, superposition of wild type (yellow) and
triple mutant (gray) ER LBD structures near the mutated
residues. The ligand is anchored by His^524 that interacts with
the carboxyl group of Glu^419, a residue from L5-6. This
glutamate contacts both the N-terminal end of H3 (Glu^339) and
the C-terminal end of H11 (Lys^531). The hydrogen bond network
connecting the estradiol O17, His^524 and Glu^419, Glu^339,
Lys^531 in the wild type structure is shown. The effect of the
C417S and C530S mutations are to shorten by one turn the
N-terminal end of H3 and the C-terminal end of H11,
respectively. This leads to the disruption of the hydrogen bond
network. To confirm the relevance of this network, Glu^339,
Glu^419, and Lys^531 were mutated in alanines and compared with
Cys Ser mutant
receptor in transactivation assays.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2001,
276,
15059-15065)
copyright 2001.
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