The assembly of a GTPase-kinase signalling complex by a bacterial catalytic scaffold

Andrey S. Selyunin, Sarah E. Sutton, Bethany A. Weigele, L. Evan Reddick, Robert C. Orchard, Stefan M. Bresson, Diana R. Tomchick, Neal M. Alto

Research output: Contribution to journalArticlepeer-review

93 Scopus citations


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 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 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.

Original languageEnglish (US)
Pages (from-to)107-113
Number of pages7
Issue number7328
StatePublished - Jan 6 2011
Externally publishedYes

ASJC Scopus subject areas

  • General


Dive into the research topics of 'The assembly of a GTPase-kinase signalling complex by a bacterial catalytic scaffold'. Together they form a unique fingerprint.

Cite this