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Crystal structure of EPEC effector NleB in complex with FADD death domainCrystal structure of EPEC effector NleB in complex with FADD death domain
Structural highlights
Disease[FADD_HUMAN] Defects in FADD are the cause of infections recurrent associated with encephalopathy hepatic dysfunction and cardiovascular malformations (IEHDCM) [MIM:613759]. A condition with biological features of autoimmune lymphoproliferative syndrome such as high-circulating CD4(-)CD8(-)TCR-alpha-beta(+) T-cell counts, and elevated IL10 and FASL levels. Affected individuals suffer from recurrent, stereotypical episodes of fever, encephalopathy, and mild liver dysfunction sometimes accompanied by generalized seizures. The episodes can be triggered by varicella zoster virus (VZV), measles mumps rubella (MMR) attenuated vaccine, parainfluenza virus, and Epstein-Barr virus (EBV).[1] Function[FADD_HUMAN] Apoptotic adaptor molecule that recruits caspase-8 or caspase-10 to the activated Fas (CD95) or TNFR-1 receptors. The resulting aggregate called the death-inducing signaling complex (DISC) performs caspase-8 proteolytic activation. Active caspase-8 initiates the subsequent cascade of caspases mediating apoptosis. Involved in interferon-mediated antiviral immune response, playing a role in the positive regulation of interferon signaling.[2] [3] [4] [5] Publication Abstract from PubMedEnteropathogenic E. coli NleB and related type III effectors catalyze arginine GlcNAcylation of death domain (DD) proteins to block host defense, but the underlying mechanism is unknown. Here we solve crystal structures of NleB alone and in complex with FADD-DD, UDP, and Mn(2+) as well as NleB-GlcNAcylated DDs of TRADD and RIPK1. NleB adopts a GT-A fold with a unique helix-pair insertion to hold FADD-DD; the interface contacts explain the selectivity of NleB for certain DDs. The acceptor arginine is fixed into a cleft, in which Glu253 serves as a base to activate the guanidinium. Analyses of the enzyme-substrate complex and the product structures reveal an inverting sugar-transfer reaction and a detailed catalytic mechanism. These structural insights are validated by mutagenesis analyses of NleB-mediated GlcNAcylation in vitro and its function in mouse infection. Our study builds a structural framework for understanding of NleB-catalyzed arginine GlcNAcylation of host death domain. Structural and Functional Insights into Host Death Domains Inactivation by the Bacterial Arginine GlcNAcyltransferase Effector.,Ding J, Pan X, Du L, Yao Q, Xue J, Yao H, Wang DC, Li S, Shao F Mol Cell. 2019 Apr 3. pii: S1097-2765(19)30232-1. doi:, 10.1016/j.molcel.2019.03.028. PMID:30979585[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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