Structure of a β-TrCP1-Skp1-β-Catenin Complex

Abstract

The SCF ubiquitin ligases catalyze protein ubiquitination in diverse cellular processes. SCFs bind substrates through the interchangeable F box protein subunit, with the >70 human F box proteins allowing the recognition of a wide range of substrates. The F box protein beta-TrCP1 recognizes the doubly phosphorylated DpSGphiXpS destruction motif, present in beta-catenin and IkappaB, and directs the SCF(beta-TrCP1) to ubiquitinate these proteins at specific lysines. The 3.0 A structure of a beta-TrCP1-Skp1-beta-catenin complex reveals the basis of substrate recognition by the beta-TrCP1 WD40 domain. The structure, together with the previous SCF(Skp2) structure, leads to the model of SCF catalyzing ubiquitination by increasing the effective concentration of the substrate lysine at the E2 active site. The model's prediction that the lysine-destruction motif spacing is a determinant of ubiquitination efficiency is confirmed by measuring ubiquitination rates of mutant beta-catenin peptides, solidifying the model and also providing a mechanistic basis for lysine selection.

Cdc25A phosphatase: combinatorial phosphorylation, ubiquitylation and proteolysis

“…According to this 'Zip' model, both kind of serines, those involved in the physical bTrCP binding and those that prime the phosphorylation of bTrCP binding motif, are essential for the recruitment of the ligase. We have demonstrated that the Cdc25A DSG motif is sufficient to recruit bTrCP, in agreement with the structure of SCF bTrCP / b-catenin recently published (Wu et al, 2003). Moreover, the finding that mutation in the upstream Chk1 site (Ser 76) results in the loss of interaction between Cdc25A and SCF bTrCP (our unpublished results) seems to approach Cdc25A to b-catenin degradation mechanism.…”

Interaction of Epstein-Barr Virus Latent Membrane Protein 1 with SCFHOS/β-TrCP E3 Ubiquitin Ligase Regulates Extent of NF-κB Activation

“…This positioning model predicts an optimal spacing between a degradation motif and a lysine residue as a key characteristic of a bona fide SCF substrate. Indeed, efficient ubiquitination of ␤-catenin-derived phosphopeptide by SCF ␤-TrCP1 requires such specific spacing (52). Our data showing that LMP1-95-8 stability is not regulated by SCF HOS E3 ubiquitin ligase unless lysine residues are introduced at optimal distance from non-canonical HOS recognition sites within LMP1 are in agreement with this positioning model.…”

“…2B). Seven WD40 domains of ␤-TrCP form a funnel-like structure with a channel that accommodates phosphorylated serines, which constitute a destruction motif within a substrate (52). The existence of additional twists of polypeptide chain between Ser-350 and Ser-366 within the non-canonical DSG(X) 14 S motif of LMP1 (shaded in Fig.…”

“…The recently solved SCF ␤-TrCP1 structure predicts that efficiency of ubiquitination by this ligase depends on the location of the ubiquitin-accepting lysine(s) relative to the destruction motif (52). LMP1-95-8 contains a single lysine residue (Lys-330) that is not essential for its ubiquitination (38).…”

Multisite protein modification and intramolecular signaling

“…Fourth, one module can contain more than one site for modification recognition (Figure 4d). For example, more than one phosphate are needed for optimal recognition by the MH2 domain of Smad2 or the WD40 domain of b-TrCP (Wu et al, 2003). Finally, modifications at different sites on a protein may cooperate to interact with one binding pocket in an allovalent manner (Figure 4e), as demonstrated for the recognition of six phosphorylation sites on the CDK inhibitor Sic1 by the SCF Cdc4 ubiquitin ligase (Orlicky et al, 2003).…”