PDBsum entry 3pcs

Protein transport/transferase

PDB id: 3pcs

Contents

Protein chains

350 a.a.

14 a.a.

12 a.a.

13 a.a.

Ligands

VAL-LEU-ASP-VAL-LEU-LYS-PHE-TYR-ASP-SER

References listed in PDB file

Key reference

• Title: The assembly of a gtpase-Kinase signalling complex by a bacterial catalytic scaffold.
• Authors: A.S.Selyunin, S.E.Sutton, B.A.Weigele, L.E.Reddick, R.C.Orchard, S.M.Bresson, D.R.Tomchick, N.M.Alto.
• Ref.: Nature, 2011, 469, 107-111.
• PubMed id: 21170023

Abstract

The fidelity and specificity of information flow within a cell is controlled by scaffolding proteins that assemble and link enzymes into signalling circuits. These circuits can be inhibited by bacterial effector proteins that post-translationally modify individual pathway components. However, there is emerging evidence that pathogens directly organize higher-order signalling networks through enzyme scaffolding, and the identity of the effectors and their mechanisms of action are poorly understood. Here we identify the enterohaemorrhagic Escherichia coli O157:H7 type III effector EspG as a regulator of endomembrane trafficking using a functional screen, and report ADP-ribosylation factor (ARF) GTPases and p21-activated kinases (PAKs) as its relevant host substrates. The 2.5 Å crystal structure of EspG in complex with ARF6 shows how EspG blocks GTPase-activating-protein-assisted GTP hydrolysis, revealing a potent mechanism of GTPase signalling inhibition at organelle membranes. In addition, the 2.8 Å crystal structure of EspG in complex with the autoinhibitory Iα3-helix of PAK2 defines a previously unknown catalytic site in EspG and provides an allosteric mechanism of kinase activation by a bacterial effector. Unexpectedly, ARF and PAKs are organized on adjacent surfaces of EspG, indicating its role as a 'catalytic scaffold' that effectively reprograms cellular events through the functional assembly of GTPase-kinase signalling complex.