title: Structural insights into a unique Legionella pneumophila effector LidA recognizing both GDP and GTP bound Rab1 in their active state.
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.
authors.affiliation: State Key Laboratory of Microbial Technology, Shandong University, Jinan, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Cheng
authors.forename: Kun
authors.initials: K
authors.lastname: Yin
authors.forename: Defen
authors.initials: D
authors.lastname: Lu
authors.forename: Bingqing
authors.initials: B
authors.lastname: Li
authors.forename: Deyu
authors.initials: D
authors.lastname: Zhu
authors.forename: Yuzhen
authors.initials: Y
authors.lastname: Chen
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.forename: Sujuan
authors.initials: S
authors.lastname: Xu
authors.forename: Jijie
authors.initials: J
authors.lastname: Chai
authors.forename: Lichuan
authors.initials: L
authors.lastname: Gu
mesh_terms: D000595:Amino Acid Sequence; D003460:Crystallization; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000737:chemistry / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D006801:Humans; D016952:Legionella pneumophila / Q000378:metabolism / Q000472:pathogenicity*; D008969:Molecular Sequence Data; D011485:Protein Binding; D017433:Protein Structure, Secondary; D020539:Sequence Analysis, Protein; D020761:rab1 GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors
chemical_list: D020730:Guanine Nucleotide Dissociation Inhibitors; D020662:Guanine Nucleotide Exchange Factors; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D020761:rab1 GTP-Binding Proteins