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PDBsum entry 2egk
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Protein binding
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PDB id
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2egk
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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 autoinhibitory pdz domain of tamalin: implications for metabotropic glutamate receptor trafficking regulation.
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Authors
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T.Sugi,
T.Oyama,
T.Muto,
S.Nakanishi,
K.Morikawa,
H.Jingami.
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Ref.
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EMBO J, 2007,
26,
2192-2205.
[DOI no: ]
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PubMed id
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Abstract
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Metabotropic glutamate receptors (mGluRs) function as neuronal G-protein-coupled
receptors and this requires efficient membrane targeting through associations
with cytoplasmic proteins. However, the molecular mechanism regulating mGluR
cell-surface trafficking remains unknown. We report here that mGluR trafficking
is controlled by the autoregulatory assembly of a scaffold protein Tamalin. In
the absence of mGluR, Tamalin self-assembles into autoinhibited conformations,
through its PDZ domain and C-terminal intrinsic ligand motif. X-ray
crystallographic analyses visualized integral parts of the oligomeric
self-assemblies of Tamalin, which require not only the novel hydrophobic
dimerization interface but also canonical and noncanonical PDZ/ligand
autoinhibitory interactions. The mGluR cytoplasmic region can competitively bind
to Tamalin at a higher concentration, disrupting weak inhibitory interactions.
The atomic view of mGluR association suggests that this rearrangement is
dominated by electrostatic attraction and repulsion. We also observed in
mammalian cells that the association liberates the intrinsic ligand toward a
motor protein receptor, thereby facilitating mGluR cell-surface trafficking. Our
study suggests a novel regulatory mechanism of the PDZ domain, by which Tamalin
switches between the trafficking-inhibited and -active forms depending on mGluR
association.
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Figure 2.
Figure 2 mGluR binding disrupts the autoinhibitory assemblies of
Tamalin to liberate the Intrinsic ligand. (A) Schematic
representation of the domain structure of Tamalin. Molecules
identified as binding partners and the series of constructs used
in this study are depicted. (B, C) Yeast two-hybrid assays of
hetero- (B) and homotypic (C) interactions of Tamalin. The
independent mating cultures were spotted and then assayed for
 -gal
activity. (D) Disruption of the autoinhibitory assembly of
Tamalin by the binding of the mGluR5 C-terminal peptide. We
utilized a pBridge vector (Clontech) instead of pAS2-1, in which
the mGluR5 C-terminus was cloned or not into second multiple
cloning site.
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Figure 7.
Figure 7 Role of the electrostatic effect in the mGluR
C-terminus/Tamalin PDZ domain interaction. Overall structure (A)
and a close-up view (B) of the Tamalin PDZ-mGluR5 C-terminus
complex. (A) The orientation of the PDZ dimers in the side view
is identical to that in Figure 4A. (C) Electrostatic surface
potential from approximately -10k[B] T^-1 (red) to +10k[B] T^-1
(blue). The negative charge of Glu114, which may contribute to
the electrostatic interaction with mGluR5, is indicated by an
arrow. (D) SPR analyses of the binding of the mGluRs and Tamalin
C-termini to the Glu114Lys PDZ mutant.
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The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
EMBO J
(2007,
26,
2192-2205)
copyright 2007.
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