 |
PDBsum entry 2qkt
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Peptide binding protein
|
PDB id
|
|
|
|
2qkt
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Dynamic scaffolding in a g protein-Coupled signaling system.
|
|
|
Authors
|
|
P.Mishra,
M.Socolich,
M.A.Wall,
J.Graves,
Z.Wang,
R.Ranganathan.
|
|
|
Ref.
|
|
Cell, 2007,
131,
80-92.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
The INAD scaffold organizes a multiprotein complex that is essential for proper
visual signaling in Drosophila photoreceptor cells. Here we show that one of the
INAD PDZ domains (PDZ5) exists in a redox-dependent equilibrium between two
conformations--a reduced form that is similar to the structure of other PDZ
domains, and an oxidized form in which the ligand-binding site is distorted
through formation of a strong intramolecular disulfide bond. We demonstrate
transient light-dependent formation of this disulfide bond in vivo and find that
transgenic flies expressing a mutant INAD in which PDZ5 is locked in the reduced
state display severe defects in termination of visual responses and visually
mediated reflex behavior. These studies demonstrate a conformational switch
mechanism for PDZ domain function and suggest that INAD behaves more like a
dynamic machine rather than a passive scaffold, regulating signal transduction
at the millisecond timescale through cycles of conformational change.
|
|
|
|
|
|
|
|
Figure 1.
Figure 1. Scaffolding in Drosophila Vision
(A)
Scaffolding in Drosophila vision. Photon absorption by rhodopsin
(1) sequentially activates Gqα (2), PLC-β (3), and TRP cation
channels (4). Calcium influx (5) activates an eye-specific
kinase (eye-PKC, 6) which phosphorylates the TRP channel (7) and
the INAD scaffold (in red, 8). Through its PDZ domains, INAD
assembles a core macromolecular complex involving PLC-β, TRP,
and eye-PKC.
(B) Structural overlay of three previously
characterized PDZ domains (PDB codes 1BE9, 1G9O, and 2F5Y).
(C) The atomic structure of PDZ5 shows overall similarity in the
β sheets, but significant conformational changes in both α
helices (see Figure S1 for quantitation). Examination of the
2F[o] − F[c] electron density at 1σ indicates the presence of
a disulfide bond between cysteines 606 and 645.
(D)
Sequence alignment of the PDZ domains shown. The color code
corresponds to the structures in (B) and (C); the positions of
the two cysteines are highlighted in the alignment.
|
|
Figure 3.
Figure 3. A Two-State Model for INAD PDZ5
A detailed
view of the binding pocket in oxidized and reduced states of
INAD PDZ5 (A) and in the C645S mutant structure (B). Key
specificity-determining residues (F642 and F649) on the α2
helix adopt significantly different conformations in the
oxidized and reduced states; the C645S mutant is effectively
locked in the reduced state structure.
|
|
|
|
|
|
The above figures are
reprinted
by permission from Cell Press:
Cell
(2007,
131,
80-92)
copyright 2007.
|
|
|
|
|
|
|
