Abstract
The TNFR1-associated death domain protein (TRADD) is an intracellular adaptor protein involved in various signaling pathways, such as antiapoptosis. Its C-terminal death domain (DD) is responsible for binding other DD-containing proteins including the p75 neurotrophin receptor (p75NTR). Here we present a solution structure of TRADD DD derived from high-resolution NMR spectroscopy. The TRADD DD comprises two super-secondary structures, an all-helix Greek key motif and a β-hairpin motif flanked by two α helices, which make it unique among all known DD structures. The β-hairpin motif is essential for TRADD DD to fold into a functional globular domain. The highly-charged surface suggests a critical role of electrostatic interactions in TRADD DD-mediated signaling. This novel structure represents a new class within the DD superfamily and provides a structural basis for studying homotypic DD interactions. NMR titration revealed a direct weak interaction between TRADD DD and p75NTR DD monomers. A binding site next to the p75NTR DD homodimerization interface indicates that TRADD DD recruitment to p75NTR requires separation of the p75NTR DD homodimer, explaining the mechanism of NGF-dependent activation of p75NTR-TRADD-mediated antiapoptotic pathway in breast cancer cell.
Highlights
The death domain (DD) superfamily is one of the largest collection of structurally and functionally related protein interaction modules
The C-terminal tail of residues T305-A312 is disordered, the globular domain of TNFR1-associated death domain protein (TRADD) DD was defined with high precision
root-mean-square deviation (RMSD) to the mean coordinate for residues T201-L304 is 0.22 ± 0.05 Å for the backbone atoms and 0.70 ± 0.05 Å for all atoms. This fine result can be attributed to ~28 nuclear Overhauser effect (NOE) distance constraints per residue obtained in the 104-residue globular structure of TRADD DD (Table 1 and Fig. S1), for which nearly complete chemical shifts have been assigned
Summary
The death domain (DD) superfamily is one of the largest collection of structurally and functionally related protein interaction modules. We present a different NMR solution structure of human TRADD DD in pure water, revealing a structure not previously seen in the DD superfamily and providing a better structural basis for studying TRADD DD-mediated signaling. Results and Discussion NMR Solution Structure Determination of TRADD DD.
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