Crystal Structure and Mechanism of Activation of TANK-Binding Kinase 1

SummaryTank-binding kinase I (TBK1) plays a key role in the innate immune system by integrating signals from pattern-recognition receptors. Here, we report the X-ray crystal structures of inhibitor-bound inactive and active TBK1 determined to 2.6 Å and 4.0 Å resolution, respectively. The structures reveal a compact dimer made up of trimodular subunits containing an N-terminal kinase domain (KD), a ubiquitin-like domain (ULD), and an α-helical scaffold dimerization domain (SDD). Activation rearranges the KD into an active conformation while maintaining the overall dimer conformation. Low-resolution SAXS studies reveal that the missing C-terminal domain (CTD) extends away from the main body of the kinase dimer. Mutants that interfere with TBK1 dimerization show significantly reduced trans-autophosphorylation but retain the ability to bind adaptor proteins through the CTD. Our results provide detailed insights into the architecture of TBK1 and the molecular mechanism of activation.

Graphical AbstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► X-ray crystal structures of active and inactive human TBK1 kinase ► Structure in complex with specific inhibitors shows binding preferences ► The CTD is fully extended and constitutively interacts with adaptors ► Dimerization is required for kinase activation but not activity