In JoVE (1)

Other Publications (2)

Articles by Olga Kagan in JoVE

Other articles by Olga Kagan on PubMed

Structure of the Shigella T3SS Effector IpaH Defines a New Class of E3 Ubiquitin Ligases

Nature Structural & Molecular Biology. Dec, 2008  |  Pubmed ID: 18997778

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.

Crystal Structure of a Putative Isochorismatase Hydrolase from Oleispira Antarctica

Journal of Structural and Functional Genomics. Mar, 2012  |  Pubmed ID: 22350524

Isochorismatase-like hydrolases (IHL) constitute a large family of enzymes divided into five structural families (by SCOP). IHLs are crucial for siderophore-mediated ferric iron acquisition by cells. Knowledge of the structural characteristics of these molecules will enhance the understanding of the molecular basis of iron transport, and perhaps resolve which of the mechanisms previously proposed in the literature is the correct one. We determined the crystal structure of the apo-form of a putative isochorismatase hydrolase OaIHL (PDB code: 3LQY) from the antarctic γ-proteobacterium Oleispira antarctica, and did comparative sequential and structural analysis of its closest homologs. The characteristic features of all analyzed structures were identified and discussed. We also docked isochorismate to the determined crystal structure by in silico methods, to highlight the interactions of the active center with the substrate. The putative isochorismate hydrolase OaIHL from O. antarctica possesses the typical catalytic triad for IHL proteins. Its active center resembles those IHLs with a D-K-C catalytic triad, rather than those variants with a D-K-X triad. OaIHL shares some structural and sequential features with other members of the IHL superfamily. In silico docking results showed that despite small differences in active site composition, isochorismate binds to in the structure of OaIHL in a similar mode to its binding in phenazine biosynthesis protein PhzD (PDB code 1NF8).

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