Coupling of tandem Smad ubiquitination regulatory factor (Smurf) WW domains modulates target specificity
Coupling of tandem Smad ubiquitination regulatory factor (Smurf) WW domains modulates target specificity
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DOI：
10.1073/pnas.1003023107
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发表时间：
2010-10-26
影响因子：
11.1
通讯作者：
Forman-Kay, Julie D.
中科院分区：
文献类型：
--
作者：
Chong, P. Andrew;Lin, Hong;Forman-Kay, Julie D.
Smad泛素化调节因子2是一种E3泛素连接酶，参与了转化生长因子-β受体和其他靶点的降解。SMurf2 WW结构域识别泛素连接酶靶蛋白或与E3靶蛋白结合的接头(如Smad7)上的PPXY(PY)基序。我们先前证明了SMurf2的分离WW3结构域，而不是WW2结构域，可以直接与Smad7 PY基序结合。在这里，我们证明了WW2通过与WW3结合并与PY基序和一个新的E/D-S/T-P基序进行辅助接触来增强这种相互作用，该基序是所有Smad PY基序的N端。WW2可能增强了SMurf2对Smad蛋白的选择性。核磁共振滴定证实Smad1和Smad2与SMurf2结合，具有与Smad7结合的相同的耦合WW结构域排列。SMurf1短亚型中类似的WW结构域通过相同的偶联机制识别Smad7 PY多肽。然而，较长的S-1异构体，其在WW间结构域连接子中有额外的26个残基，仅部分能够使用耦合的WW结构域结合机制。连接子越长，与Smad7多肽的亲和力就越低。WW结构域的域间耦合增强了选择性，并能够通过异构体切换来调节相互作用。
Smad 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.