title: Structural basis of dimerization-dependent ubiquitination by the SCF(Fbx4) ubiquitin ligase.
abstract: The F-box proteins are the substrate recognition subunits of the SCF (Skp1-Cul1-Rbx1-F- box protein) ubiquitin ligase complexes that control the stability of numerous regulators in eukaryotic cells. Here we show that dimerization of the F-box protein Fbx4 is essential for SCF(Fbx4) (the superscript denotes the F-box protein) ubiquitination activity toward the telomere regulator Pin2 (also known as TRF1). The crystal structure of Fbx4 in complex with an adaptor protein Skp1 reveals an antiparallel dimer configuration in which the linker domain of Fbx4 interacts with the C-terminal substrate-binding domain of the other protomer, whereas the C-terminal domain of the protein adopts a compact alpha/beta fold distinct from those of known F-box proteins. Biochemical studies indicate that both the N-terminal domain and a loop connecting the linker and C-terminal domain of Fbx4 are critical for the dimerization and activation of the protein. Our findings provide a framework for understanding the role of F-box dimerization in the SCF-mediated ubiquitination reaction.
authors.affiliation: Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, Farmington, Connecticut 06030, USA.
authors.forename: Yunfeng
authors.initials: Y
authors.lastname: Li
authors.forename: Bing
authors.initials: B
authors.lastname: Hao
mesh_terms: D044783:F-Box Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D009097:Multienzyme Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017510:Protein Folding; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D044843:SKP Cullin F-Box Protein Ligases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D035321:Telomeric Repeat Binding Protein 1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination / Q000502:physiology
chemical_list: D044783:F-Box Proteins; C508146:FBXO4 protein, human; D009097:Multienzyme Complexes; D035321:Telomeric Repeat Binding Protein 1; D044843:SKP Cullin F-Box Protein Ligases