Structural insights into a unique Legionella pneumophila effector LidA recognizing both GDP and GTP bound Rab1 in their active state

PLoS Pathog. 2012;8(3):e1002528. doi: 10.1371/journal.ppat.1002528. Epub 2012 Mar 1.

Abstract

The intracellular pathogen Legionella pneumophila hijacks the endoplasmic reticulum (ER)-derived vesicles to create an organelle designated Legionella-containing vacuole (LCV) required for bacterial replication. Maturation of the LCV involved acquisition of Rab1, which is mediated by the bacterial effector protein SidM/DrrA. SidM/DrrA is a bifunctional enzyme having the activity of both Rab1-specific GDP dissociation inhibitor (GDI) displacement factor (GDF) and guanine nucleotide exchange factor (GEF). LidA, another Rab1-interacting bacterial effector protein, was reported to promote SidM/DrrA-mediated recruitment of Rab1 to the LCV as well. Here we report the crystal structures of LidA complexes with GDP- and GTP-bound Rab1 respectively. Structural comparison revealed that GDP-Rab1 bound by LidA exhibits an active and nearly identical conformation with that of GTP-Rab1, suggesting that LidA can disrupt the switch function of Rab1 and render it persistently active. As with GTP, LidA maintains GDP-Rab1 in the active conformation through interaction with its two conserved switch regions. Consistent with the structural observations, biochemical assays showed that LidA binds to GDP- and GTP-Rab1 equally well with an affinity approximately 7.5 nM. We propose that the tight interaction with Rab1 allows LidA to facilitate SidM/DrrA-catalyzed release of Rab1 from GDIs. Taken together, our results support a unique mechanism by which a bacterial effector protein regulates Rab1 recycling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Crystallization
  • Guanine Nucleotide Dissociation Inhibitors / chemistry
  • Guanine Nucleotide Dissociation Inhibitors / metabolism*
  • Guanine Nucleotide Exchange Factors / chemistry
  • Guanine Nucleotide Exchange Factors / metabolism*
  • Host-Pathogen Interactions*
  • Humans
  • Legionella pneumophila / metabolism
  • Legionella pneumophila / pathogenicity*
  • Molecular Sequence Data
  • Protein Binding
  • Protein Structure, Secondary
  • Sequence Analysis, Protein
  • rab1 GTP-Binding Proteins / chemistry
  • rab1 GTP-Binding Proteins / metabolism*
  • rho-Specific Guanine Nucleotide Dissociation Inhibitors

Substances

  • Guanine Nucleotide Dissociation Inhibitors
  • Guanine Nucleotide Exchange Factors
  • rho-Specific Guanine Nucleotide Dissociation Inhibitors
  • rab1 GTP-Binding Proteins