3l0m
From Proteopedia
Crystal structure of Rab1-activation domain and P4M domain of SidM/DrrA from legionella
Structural highlights
Function[DRRA_LEGPN] Virulence effector that plays a key role in hijacking the host vesicular trafficking by recruiting the small guanosine triphosphatase (GTPase) Rab1 to the cytosolic face of the Legionella-containing vacuole (LCVs). Acts as a GDP-GTP exchange factor (GEF) for the small GTPase Rab1 (RAB1A, RAB1B or RAB1C), thereby converting Rab1 to an active GTP-bound state, leading to the incorporation of Rab1 into LCVs. Also shows RabGDI displacement factor (GDF) activity; however, this probably represents a passive activity following the GEF activity. Also acts as an adenylyltransferase by mediating the addition of adenosine 5'-monophosphate (AMP) to 'Tyr-77' of host RAB1B, thereby rendering RAB1B constitutively active. Also has adenylyltransferase activity towards Rab6 and Rab35. Also displays guanylyltransferase activity by mediating the addition of guanosine 5'-monophosphate (GMP) to host RAB1B in vitro; however such activity remains uncertain in vivo. Specifically binds phosphatidylinositol 4-phosphate (PtdIns(4)P) lipids on the cytosolic surface of the phagosomal membrane shortly after infection.[1] [2] [3] Publication Abstract from PubMedBacterial pathogens deliver effector proteins with diverse biochemical activities into host cells, thereby modulating various host functions. Legionella pneumophila hijacks host vesicle trafficking to avoid phagosome-lysosome fusion, a mechanism that is dependent on the Legionella Dot/Icm type IV secretion system. SidM/DrrA, a Legionella type IV effector, is important for the interactions of Legionella-containing vacuoles with host endoplasmic reticulum-derived vesicles. SidM is the only known protein that catalyzes both the exchange of GDP for GTP and GDI displacement from small GTPase Rab1. We determined the crystal structures of SidM alone (residues 317-647) and SidM (residues 193-550) in complex with nucleotide-free WT Rab1. The SidM structure contains an N-terminal helical domain with a potential new function, a Rab1-activation domain, and a C-terminal phosphatidylinositol 4-phosphate-binding P4M domain. The Rab1-activation domain has extensive strong interactions mainly with Rab1 switch I and II regions that undergo substantial conformational changes on SidM binding. Mutations of switch-contacting residues in SidM attenuate both the nucleotide exchange and GDI displacement activities. Structural comparisons of Rab1 in the SidM complex with Rab1-GDP and Ypt1-GDP in the GDI complex identify key conformational changes that disrupt the nucleotide and GDI binding of Rab1. Further biochemical and structural analyses reveal a unique mechanism of coupled GDP release and GDI displacement likely triggered by the SidM-induced drastic displacement of switch I of Rab1. Structural mechanism of host Rab1 activation by the bifunctional Legionella type IV effector SidM/DrrA.,Zhu Y, Hu L, Zhou Y, Yao Q, Liu L, Shao F Proc Natl Acad Sci U S A. 2010 Mar 9;107(10):4699-704. Epub 2010 Feb 22. PMID:20176951[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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