Enterohaemorrhagic Escherichia Coli Exploits a Tryptophan Switch to Hijack Host F-Actin Assembly

• Published in: Structure (London) 2012-10, Vol.20 (10), p.1692-1703
• Main Authors: Aitio, Olli, Hellman, Maarit, Skehan, Brian, Kesti, Tapio, Leong, John M., Saksela, Kalle, Permi, Perttu
• Format: Article
• Language: English
• Subjects: Actins - chemistry; Amino Acid Sequence; Carrier Proteins - chemistry; Conserved Sequence; Enterohemorrhagic Escherichia coli - physiology; Escherichia coli Proteins - chemistry; HEK293 Cells; Host-Pathogen Interactions; Humans; Hydrophobic and Hydrophilic Interactions; Intracellular Signaling Peptides and Proteins; Microfilament Proteins - chemistry; Models, Molecular; Molecular Sequence Data; Nuclear Magnetic Resonance, Biomolecular; Peptide Fragments - chemistry; Protein Binding; Protein Structure, Quaternary; Protein Transport; src Homology Domains; Thermodynamics; Tryptophan - chemistry; Wiskott-Aldrich Syndrome Protein, Neuronal - chemistry
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2012.07.015

Intrinsically disordered protein (IDP)-mediated interactions are often characterized by low affinity but high specificity. These traits are essential in signaling and regulation that require reversibility. Enterohaemorrhagic Escherichia coli (EHEC) exploit this situation by commandeering host cytoskeletal signaling to stimulate actin assembly beneath bound bacteria, generating “pedestals” that promote intestinal colonization. EHEC translocates two proteins, EspFU and Tir, which form a complex with the host protein IRTKS. The interaction of this complex with N-WASP triggers localized actin polymerization. We show that EspFU is an IDP that contains a transiently α-helical N-terminus and dynamic C-terminus. Our structure shows that single EspFU repeat forms a high-affinity trimolecular complex with N-WASP and IRTKS. We demonstrate that bacterial and cellular ligands interact with IRTKS SH3 in a similar fashion, but the bacterial protein has evolved to outcompete cellular targets by utilizing a tryptophan switch that offers superior binding affinity enabling EHEC-induced pedestal formation. ► EspFU is an IDP that establishes a high-affinity complex with IRTKS and N-WASP ► Trimolecular complex structure of N-WASP GBD, EspFU R47, and IRTKS SH3 ► EspFU utilizes a W-switch to establish intermolecular Trp-Trp interaction ► W-switch translates into functional advantage of EHEC, i.e., hijacking of IRTKS/IRSp53 Enterohaemorrhagic E. coli (EHEC) translocates two proteins, EspFU and Tir, into the host cell to hijack cytoskeletal signaling. Aitio et al. show that EspFU forms a high-affinity complex with N-WASP and IRTKS and outcompetes other targets by using a tryptophan switch, offering superior binding affinity for IRTKS.