Structural Basis for Substrate Selectivity of the E3 Ligase COP1

• Published in: Structure (London) 2016-05, Vol.24 (5), p.687-696
• Main Authors: Uljon, Sacha, Xu, Xiang, Durzynska, Izabela, Stein, Sarah, Adelmant, Guillaume, Marto, Jarrod A., Pear, Warren S., Blacklow, Stephen C.
• Format: Article
• Language: English
• Subjects: Arabidopsis - enzymology; Arabidopsis Proteins - chemistry; Arabidopsis Proteins - metabolism; Binding Sites; Humans; Intracellular Signaling Peptides and Proteins - chemistry; Intracellular Signaling Peptides and Proteins - metabolism; Molecular Docking Simulation; Peptide Fragments - chemistry; Peptide Fragments - metabolism; Protein Binding; Protein-Serine-Threonine Kinases - antagonists & inhibitors; Protein-Serine-Threonine Kinases - chemistry; Protein-Serine-Threonine Kinases - metabolism; Substrate Specificity; Ubiquitin-Protein Ligases - chemistry; Ubiquitin-Protein Ligases - metabolism; WD40 Repeats
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2016.03.002

COP1 proteins are E3 ubiquitin ligases that regulate phototropism in plants and target transcription factors for degradation in mammals. The substrate-binding region of COP1 resides within a WD40-repeat domain that also binds to Trib proteins, which are adaptors for C/EBPα degradation. Here we report structures of the human COP1 WD40 domain in isolation, and complexes of the human and Arabidopsis thaliana COP1 WD40 domains with the binding motif of Trib1. The human and Arabidopsis WD40 domains are seven-bladed β propellers with an inserted loop on the bottom face of the first blade. The Trib1 peptide binds in an extended conformation to a highly conserved surface on the top face of the β propeller, indicating a general mode for recognition of peptide motifs by COP1. Together, these studies identify the structural basis and key interactions for motif recognition by COP1, and hint at how Trib1 autoinhibition is overcome to target C/EBPα for degradation. [Display omitted] •X-Ray structures reported for human and plant COP1 β-propeller-peptide complexes•Trib1 peptides bind to a conserved surface on the top face of the propeller•Structures reveal a universal mechanism for motif recognition by COP1•Competition binding assays confirm importance of consensus VP sequence COP1 proteins are E3 ubiquitin ligases that regulate phototropism in plants and target transcription factors for degradation in mammals. The substrate-binding region of COP1 resides within a WD40-repeat domain that also binds to Trib proteins, the adaptors for C/EBPα degradation. Uljon et al. identify the structural basis and key interactions for motif recognition by COP1, and hint at how Trib1 autoinhibition is overcome to target C/EBPα for degradation.