Structural basis for effector transmembrane domain recognition by type VI secretion system chaperones Academic Article uri icon

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abstract

  • Type VI secretion systems (T6SSs) deliver antibacterial effector proteins between neighboring bacteria. Many effectors harbor N-terminal transmembrane domains (TMDs) implicated in effector translocation across target cell membranes. However, the distribution of these TMD-containing effectors remains unknown. Here, we discover prePAAR, a conserved motif found in over 6000 putative TMD-containing effectors encoded predominantly by 15 genera of Proteobacteria. Based on differing numbers of TMDs, effectors group into two distinct classes that both require a member of the Eag family of T6SS chaperones for export. Co-crystal structures of class I and class II effector TMD-chaperone complexes from Salmonella Typhimurium and Pseudomonas aeruginosa, respectively, reveals that Eag chaperones mimic transmembrane helical packing to stabilize effector TMDs. In addition to participating in the chaperone-TMD interface, we find that prePAAR residues mediate effector-VgrG spike interactions. Taken together, our findings reveal mechanisms of chaperone-mediated stabilization and secretion of two distinct families of T6SS membrane protein effectors.

authors

  • Ahmad, Shehryar
  • Tsang, Kara K
  • Sachar, Kartik
  • Quentin, Dennis
  • Tashin, Tahmid M
  • Bullen, Nathan P
  • Raunser, Stefan
  • McArthur, Andrew
  • Prehna, Gerd
  • Whitney, John

publication date

  • December 15, 2020

published in