title: The TLR signalling adaptor TRIF/TICAM-1 has an N-terminal helical domain with structural similarity to IFIT proteins.
abstract: TRIF/TICAM-1 (TIR domain-containing adaptor inducing interferon-β/TIR domain-containing adaptor molecule 1) is the adaptor protein in the Toll-like receptor (TLR) 3 and 4 signalling pathway that leads to the production of type 1 interferons and cytokines. The signalling involves TIR (Toll/interleukin-1 receptor) domain-dependent TRIF oligomerization. A protease-resistant N-terminal region is believed to be involved in self-regulation of TRIF by interacting with its TIR domain. Here, the structural and functional characterization of the N-terminal domain of TRIF (TRIF-NTD) comprising residues 1-153 is reported. The 2.22 Å resolution crystal structure was solved by single-wavelength anomalous diffraction (SAD) using selenomethionine-labelled crystals of TRIF-NTD containing two additional introduced Met residues (TRIF-NTDA66M/L113M). The structure consists of eight antiparallel helices that can be divided into two subdomains, and the overall fold shares similarity to the interferon-induced protein with tetratricopeptide repeats (IFIT) family of proteins, which are involved in both the recognition of viral RNA and modulation of innate immune signalling. Analysis of TRIF-NTD surface features and the mapping of sequence conservation onto the structure suggest several possible binding sites involved in either TRIF auto-regulation or interaction with other signalling molecules or ligands. TRIF-NTD suppresses TRIF-mediated activation of the interferon-β promoter, as well as NF-κB-dependent reporter-gene activity. These findings thus identify opportunities for the selective targeting of TLR3- and TLR4-mediated inflammation.
authors: School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Queensland 4072, Australia.
authors: M Obayed
authors: MO
authors: Ullah
authors: Thomas
authors: T
authors: Ve
authors: Matthew
authors: M
authors: Mangan
authors: Mohammed
authors: M
authors: Alaidarous
authors: Matthew J
authors: MJ
authors: Sweet
authors: Ashley
authors: A
authors: Mansell
authors: Bostjan
authors: B
authors: Kobe
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D057809:HEK293 Cells; D006801:Humans; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000737:chemistry* / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D015398:Signal Transduction; D051193:Toll-Like Receptors / Q000378:metabolism
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; C110985:IFIT5 protein, human; D009363:Neoplasm Proteins; C470409:TICAM1 protein, human; D051193:Toll-Like Receptors
keywords: IFIT proteins; TICAM-1; TRIF; Toll-like receptor adaptor protein; innate immunity; tetratricopeptide repeat