Structural Insights into Linear Tri-ubiquitin Recognition by A20-Binding Inhibitor of NF-κB, ABIN-2.

Recognition of linear polyubiquitin by specific ubiquitin-binding proteins plays an important role in mediating nuclear factor-κB (NF-κB) signaling. A20 binding proteins, ABINs, recognize linear polyubiquitin and A20 through UBAN and AHD1, respectively, for the inhibition of NF-κB activation. Here we report the crystal structure of the AHD1-UBAN fragment of ABIN2 ...
in complex with linear tri-ubiquitin, which reveals a 2:1 stoichiometry of the complex. Structural analyses together with mutagenesis, pull-down, and isothermal titration calorimetry assays show that the hABIN2:tri-ubiquitin interaction is mainly through the primary ubiquitin-binding site, and also through the secondary ubiquitin-binding site under a high local protein concentration. Surprisingly, three ubiquitin units could form a right-handed helical trimer to bridge two ABIN2 dimers. The residues around the M1-linkage are crucial for ABIN2 to recognize tri-ubiquitin. The tri-ubiquitin bridging two ABIN2 dimers model suggests a possible higher-order signaling complex assembled between M1-linked polyubiquitinated proteins, ubiquitin-binding proteins, and effector signaling proteins in signal transduction.
Mesh Terms:
Adaptor Proteins, Signal Transducing, Binding Sites, Crystallography, X-Ray, Humans, Models, Molecular, Polyubiquitin, Protein Binding, Protein Structure, Secondary, Signal Transduction, Tumor Necrosis Factor alpha-Induced Protein 3
Structure
Date: Dec. 03, 2016
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