2kxq | pdb_00002kxq
Solution Structure of Smurf2 WW2 and WW3 bound to Smad7 PY motif containing peptide
Structural highlights
Function[SMUF2_HUMAN] E3 ubiquitin-protein ligase which accepts ubiquitin from an E2 ubiquitin-conjugating enzyme in the form of a thioester and then directly transfers the ubiquitin to targeted substrates. Interacts with SMAD1 and SMAD7 in order to trigger their ubiquitination and proteasome-dependent degradation. In addition, interaction with SMAD7 activates autocatalytic degradation, which is prevented by interaction with SCYE1. Forms a stable complex with the TGF-beta receptor-mediated phosphorylated SMAD2 and SMAD3. In this way, SMAD2 may recruit substrates, such as SNON, for ubiquitin-mediated degradation. Enhances the inhibitory activity of SMAD7 and reduces the transcriptional activity of SMAD2. Coexpression of SMURF2 with SMAD1 results in considerable decrease in steady-state level of SMAD1 protein and a smaller decrease of SMAD2 level.[1] [2] Publication Abstract from PubMedSmad ubiquitination regulatory factor 2 (Smurf2) is an E3 ubiquitin ligase that participates in degradation of TGF-beta receptors and other targets. Smurf2 WW domains recognize PPXY (PY) motifs on ubiquitin ligase target proteins or on adapters, such as Smad7, that bind to E3 target proteins. We previously demonstrated that the isolated WW3 domain of Smurf2, but not the WW2 domain, can directly bind to a Smad7 PY motif. We show here that the WW2 augments this interaction by binding to the WW3 and making auxiliary contacts with the PY motif and a novel E/D-S/T-P motif, which is N-terminal to all Smad PY motifs. The WW2 likely enhances the selectivity of Smurf2 for the Smad proteins. NMR titrations confirm that Smad1 and Smad2 are bound by Smurf2 with the same coupled WW domain arrangement used to bind Smad7. The analogous WW domains in the short isoform of Smurf1 recognize the Smad7 PY peptide using the same coupled mechanism. However, a longer Smurf1 isoform, which has an additional 26 residues in the inter-WW domain linker, is only partially able to use the coupled WW domain binding mechanism. The longer linker results in a decrease in affinity for the Smad7 peptide. Interdomain coupling of WW domains enhances selectivity and enables the tuning of interactions by isoform switching. Coupling of tandem Smad ubiquitination regulatory factor (Smurf) WW domains modulates target specificity.,Chong PA, Lin H, Wrana JL, Forman-Kay JD Proc Natl Acad Sci U S A. 2010 Oct 26;107(43):18404-9. Epub 2010 Oct 11. PMID:20937913[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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