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PDBsum entry 1iu2
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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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Supramodular structure and synergistic target binding of the n-Terminal tandem pdz domains of psd-95.
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Authors
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J.F.Long,
H.Tochio,
P.Wang,
J.S.Fan,
C.Sala,
M.Niethammer,
M.Sheng,
M.Zhang.
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Ref.
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J Mol Biol, 2003,
327,
203-214.
[DOI no: ]
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PubMed id
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Abstract
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PDZ domain proteins play critical roles in binding, clustering and subcellular
targeting of membrane receptors and ion channels. PDZ domains in multi-PDZ
proteins often are arranged in groups with highly conserved spacing and
intervening sequences; however, the functional significance of such tandem
arrangements of PDZs is unclear. We have solved the three-dimensional structure
of the first two PDZ domains of postsynaptic density protein-95 (PSD-95 PDZ1 and
PDZ2), which are closely linked to each other in the PSD-95 family of scaffold
proteins. The two PDZs have limited freedom of rotation and their C-terminal
peptide-binding grooves are aligned with each other with an orientation
preference for binding to pairs of C termini extending in the same direction.
Increasing the spacing between PDZ1 and PDZ2 resulted in decreased binding
between PDZ12 and its dimeric targets. The same mutation impaired the functional
ability of PSD-95 to cluster Kv1.4 potassium channels in heterologous cells. The
data presented provide a molecular basis for preferential binding of PSD-95 to
multimeric membrane proteins with appropriate C-terminal sequences.
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Figure 1.
Figure 1. Structure of PSD-95 PDZ1 determined by NMR
spectroscopy. (A) Stereoview showing the best-fit superposition
of the backbone atoms (N, C^a, and C') of the final 20
structures of PSD-95 PDZ1. The structures are superimposed
against the average structure using the residues 64-148. The
structural statistics are summarized in Table 1. (B) Ribbon
diagram presentation of PSD-95 PDZ1. The secondary structure
elements are labelled following the scheme used in the crystal
structure of PSD-95 PDZ3. [7] (C) Comparison of the 3D
structures of PDZ1 and PDZ2 of PSD-95. The backbone traces (N,
C^a, and C') of PDZ1 (gold) and PDZ2 (yellow) are superimposed.
The two structures were fit to each other by excluding the
GLGF-loop, bB/bC loop and the two termini. The rmsd between the
backbones of the two PDZ domains is 1.35 Å.
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Figure 5.
Figure 5. Functional role of conformation-restrained tandem
PDZ repeats in PSD-95. (A) Extending the PDZ12 linker by
introducing flexible amino acid residues reduces the size of the
Kv1.4 channel clusters mediated by N-PDZ12. Myc-tagged
constructs N-PDZ1-2 wild-type (N-PDZ12), the deletion mutant of
N-PDZ12 (N-PDZ12Del) and the insertion mutant of N-PDZ12
(N-PDZ1-2Ins) were co-transfected in COS7 cells with potassium
channel subunit Kv1.4. Cells cotransfected with different
constructs, as indicated, were fixed two days after transfection
and stained with Kv1.4 antibodies to visualize the potassium
channel clusters. The schematics of the deletions and insertion
mutations used in this study are shown. Insets show
higher-magnification views of Kv1.4 clusters. (B) Frequency
distribution (left) and mean values (right) of Kv1.4 cluster
areas mediated by N-PDZ12, N-PDZ12(Del) and N-PDZ12(Ins),
measured from at least ten cells for each construct. The scale
bars represent 5 µm or 15 µm for the insets. An
asterisk (*) indicates significance at p <0.01 in an unpaired,
two-tailed Student's t-test.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2003,
327,
203-214)
copyright 2003.
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