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Structural basis for SidJ-catalyzed polyglutamylation of the SidE all-in-one ubiquitin ligases


EMSL Project ID
51520

Abstract

Enzymes with a protein kinase fold transfer phosphate from ATP to substrates in a process known as phosphorylation. We have discovered that the Legionella meta-effector SidJ adopts a protein kinase fold, yet unexpectedly catalyzes protein polyglutamylation. SidJ is activated by host cell calmodulin (CaM) to polyglutamylate the SidE-family of all-in-one ubiquitin (Ub) ligases. Crystal structures of the SidJ-CaM complex reveal a protein kinase fold that catalyzes ATP-dependent isopeptide bond formation between the amino group of free glutamate and the gamma-carboxyl group of an active site glutamate in SidE. We show that SidJ polyglutamylation of SidE and the consequent inactivation of Ub ligase activity is required for successful Legionella replication in a eukaryotic host. Although our results have uncovered the mechanism by which SidJ inactivates the SidE Ub ligases, we lack structural information as to how an enzyme with a protein kinase fold catalyzes polyglutamylation. We have evidence that the SidJ/CaM:AMP-SidE intermediate complex is stable and our preliminary cryoEM images suggests that additional data collection has a high probability of obtaining a near atomic resolution structure of the complex.

Project Details

Start Date
2020-06-15
End Date
2021-03-17
Status
Closed

Team

Principal Investigator

Vincent Tagliabracci
Institution
University of Texas Southwestern Medical Center

Team Members

Adam Osinski
Institution
University of Texas Southwestern Medical Center

Yang Li
Institution
University of Texas Southwestern Medical Center

Zhe Chen
Institution
University of Texas Southwestern Medical Center

Irina El Khoury
Institution
Environmental Molecular Sciences Laboratory