PDBsum entry 2qkt

Peptide binding protein

PDB id: 2qkt

Contents

Protein chains

85 a.a. *

Waters ×153

* Residue conservation analysis

PDB id:

2qkt

Name:

Peptide binding protein

Title:

Crystal structure of the 5th pdz domain of inad

Structure:

Inactivation-no-after-potential d protein. Chain: a, b. Fragment: 5th pdz domain. Engineered: yes

Source:

Drosophila melanogaster. Fruit fly. Organism_taxid: 7227. Gene: inad. Expressed in: escherichia coli bl21(de3). Expression_system_taxid: 469008.

Resolution:

2.05Å R-factor: 0.224 R-free: 0.242

Authors:

R.Ranganathan,M.Socolich

Key ref:

P.Mishra et al. (2007). Dynamic scaffolding in a g protein-coupled signaling system. Cell, 131, 80-92. PubMed id: 17923089 DOI: 10.1016/j.cell.2007.07.037

Date:

11-Jul-07 Release date: 06-Nov-07

Protein chains

Q24008  (INAD_DROME) -  Inactivation-no-after-potential D protein from Drosophila melanogaster

Seq: 674 a.a.

Struc: 85 a.a.

DOI no: 10.1016/j.cell.2007.07.037

Cell 131:80-92 (2007)

PubMed id: 17923089

Dynamic scaffolding in a g protein-coupled signaling system.

P.Mishra, M.Socolich, M.A.Wall, J.Graves, Z.Wang, R.Ranganathan.

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.

Selected figure(s)

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.

Figures were selected by an automated process.