Structure of the Shigella T3SS effector IpaH defines a new class of E3 ubiquitin ligases.
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.
Singer
Alexander U
AU
Ontario Centre for Structural Proteomics, Banting and Best Department for Medical Research, University of Toronto, C.H. Best Institute, Toronto, Ontario M5G1L5, Canada.
Rohde
John R
JR
Lam
Robert
R
Skarina
Tatiana
T
Kagan
Olga
O
Dileo
Rosa
R
Chirgadze
Nickolay Y
NY
Cuff
Marianne E
ME
Joachimiak
Andrzej
A
Tyers
Mike
M
Sansonetti
Philippe J
PJ
Parsot
Claude
C
Savchenko
Alexei
A
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*
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D050505:Mutant Proteins; C063500:ipaH protein, Shigella flexneri; D044767:Ubiquitin-Protein Ligases