title: Structure of the Shigella T3SS effector IpaH defines a new class of E3 ubiquitin ligases.
abstract: IpaH proteins are E3 ubiquitin ligases delivered by the type III secretion apparatus into host cells upon infection of humans by the Gram-negative pathogen Shigella flexneri. These proteins comprise a variable leucine-rich repeat-containing N-terminal domain and a conserved C-terminal domain harboring an invariant cysteine residue that is crucial for activity. IpaH homologs are encoded by diverse animal and plant pathogens. Here we demonstrate that the IpaH C-terminal domain carries the catalytic activity for ubiquitin transfer and that the N-terminal domain carries the substrate specificity. The structure of the IpaH C-terminal domain, determined to 2.65-A resolution, represents an all-helical fold bearing no resemblance to previously defined E3 ubiquitin ligases. The conserved and essential cysteine residue lies on a flexible, surface-exposed loop surrounded by conserved acidic residues, two of which are crucial for IpaH activity.
authors.affiliation: Ontario Centre for Structural Proteomics, Banting and Best Department for Medical Research, University of Toronto, C.H. Best Institute, Toronto, Ontario M5G1L5, Canada.
authors.forename: Alexander U
authors.initials: AU
authors.lastname: Singer
authors.forename: John R
authors.initials: JR
authors.lastname: Rohde
authors.forename: Robert
authors.initials: R
authors.lastname: Lam
authors.forename: Tatiana
authors.initials: T
authors.lastname: Skarina
authors.forename: Olga
authors.initials: O
authors.lastname: Kagan
authors.forename: Rosa
authors.initials: R
authors.lastname: Dileo
authors.forename: Nickolay Y
authors.initials: NY
authors.lastname: Chirgadze
authors.forename: Marianne E
authors.initials: ME
authors.lastname: Cuff
authors.forename: Andrzej
authors.initials: A
authors.lastname: Joachimiak
authors.forename: Mike
authors.initials: M
authors.lastname: Tyers
authors.forename: Philippe J
authors.initials: PJ
authors.lastname: Sansonetti
authors.forename: Claude
authors.initials: C
authors.lastname: Parsot
authors.forename: Alexei
authors.initials: A
authors.lastname: Savchenko
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000942:Antigens, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000378:metabolism; D020125:Mutation, Missense; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D050505:Mutant Proteins; C063500:ipaH protein, Shigella flexneri; D044767:Ubiquitin-Protein Ligases