Backbone ¹H, ¹⁵N, and ¹³C resonance assignments and secondary structure of the Tollip CUE domain

The Toll-interacting protein (Tollip) is a negative regulator of the Toll-like receptor (TLR)-mediated inflammation response. Tollip is a modular protein that contains an N-terminal Tom1-binding domain (TBD), a central conserved domain 2 (C2), and a C-terminal coupling of ubiquitin to endoplasmic reticulum degradation (CUE) domain. Here, we report the sequence-specific backbone ¹H, ¹⁵N, and ¹³C assignments of the human Tollip CUE domain. The CUE domain was found to be a stable dimer as determined by size-exclusion chromatography and molecular crosslinking studies. Analysis of the backbone chemical shift data indicated that the CUE domain exhibits three helical elements corresponding to 52% of the protein backbone. Circular dichroism spectrum analysis confirmed the helical nature of this domain. Comparison of the location of these helical regions with those reported for yeast CUE domains suggest differences in length for all helical elements. We expect the structural analysis presented here will be the foundation for future studies on the biological significance of the Tollip CUE domain, its molecular interactions, and the mechanisms that modulate its function during the inflammatory response.