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Legionella effector MavC targets the Ube2N~Ub conjugate for noncanonical ubiquitination.

Kedar PuvarShalini IyerJiaqi FuSebastian KennyKristos I Negrón TerónZhao-Qing LuoPeter S BrzovicRachel E KlevitChittaranjan Das
Published in: Nature communications (2020)
The bacterial effector MavC modulates the host immune response by blocking Ube2N activity employing an E1-independent ubiquitin ligation, catalyzing formation of a γ-glutamyl-ε-Lys (Gln40Ub-Lys92Ube2N) isopeptide crosslink using a transglutaminase mechanism. Here we provide biochemical evidence in support of MavC targeting the activated, thioester-linked Ube2N~ubiquitin conjugate, catalyzing an intramolecular transglutamination reaction, covalently crosslinking the Ube2N and Ub subunits effectively inactivating the E2~Ub conjugate. Ubiquitin exhibits weak binding to MavC alone, but shows an increase in affinity when tethered to Ube2N in a disulfide-linked substrate that mimics the charged E2~Ub conjugate. Crystal structures of MavC in complex with the substrate mimic and crosslinked product provide insights into the reaction mechanism and underlying protein dynamics that favor transamidation over deamidation, while revealing a crucial role for the structurally unique insertion domain in substrate recognition. This work provides a structural basis of ubiquitination by transglutamination and identifies this enzyme's true physiological substrate.
Keyphrases
  • structural basis
  • cancer therapy
  • immune response
  • small molecule
  • amino acid
  • dendritic cells
  • regulatory t cells
  • genome wide
  • drug delivery
  • gene expression
  • dna methylation
  • toll like receptor