PMID: 24311583

Authors:

Ullah MO, Ve T, Mangan M, Alaidarous M, Sweet MJ, Mansell A, Kobe B

Title:

The TLR signalling adaptor TRIF/TICAM-1 has an N-terminal helical domain with structural similarity to IFIT proteins.

Journal:

Acta Crystallogr D Biol Crystallogr. 2013 Dec;69(Pt 12):2420-30. doi:, 10.1107/S0907444913022385. Epub 2013 Nov 19.

Abstract:

TRIF/TICAM-1 (TIR domain-containing adaptor inducing interferon-beta/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 A 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-NTD(A66M/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-beta promoter, as well as NF-kappaB-dependent reporter-gene activity. These findings thus identify opportunities for the selective targeting of TLR3- and TLR4-mediated inflammation.