Suprafacial orientation of the SCFCdc4 dimer accommodates multiple geometries for substrate ubiquitination
Suprafacial orientation of the SCFCdc4 dimer accommodates multiple geometries for substrate ubiquitination
复制标题
DOI：
10.1016/j.cell.2007.04.042
复制
发表时间：
2007-06-15
期刊：
影响因子：
64.5
通讯作者：
Tyers, Mike
中科院分区：
文献类型：
--
作者：
Tang, Xiaojing;Orlicky, Stephen;Tyers, Mike
SCF泛素连接酶通过F box蛋白接头亚基招募底物进行降解。WD40重复F盒蛋白，如Cdc4和β - trcp，包含一个保守的二聚化基序，称为D结构域。在这里，我们报道了酵母Cdc4和人β - trcp的D结构域原体形成一个超螺旋同型二聚体。D结构域的破坏损害了酵母SCFCdc4对CDK抑制剂Sicl和其他底物的活性。SCFCdc4二聚化对Sicl的亲和力影响不大，但明显促进泛素结合。基于小角度x射线散射测量的二聚体全息- scfcdc4配合物模型揭示了其表面结构，其中底物结合位点和E2催化位点位于同一平面，每个SCIF单体内部和之间的间距分别为64埃和102埃。这种空间变异性可以在底物和延长泛素链中容纳不同的受体赖氨酸几何形状，从而提高催化效率。
SCF ubiquitin ligases recruit substrates for degradation via F box protein adaptor subunits. WD40 repeat F box proteins, such as Cdc4 and beta-TrCP, contain a conserved dimerization motif called the D domain. Here, we report that the D domain protomers of yeast Cdc4 and human beta-TrCP form a superhelical homotypic dimer. Disruption of the D domain compromises the activity of yeast SCFCdc4 toward the CDK inhibitor Sicl and other substrates. SCFCdc4 dimerization has little effect on the affinity for Sicl but markedly stimulates ubiquitin conjugation. A model of the dimeric holo-SCFCdc4 complex based on small-angle X-ray scatter measurements reveals a suprafacial configuration, in which substrate-binding sites and E2 catalytic sites lie in the same plane with a separation of 64 angstrom within and 102 angstrom between each SCIF monomer. This spatial variability may accommodate diverse acceptor lysine geometries in both substrates and the elongating ubiquitin chain and thereby increase catalytic efficiency.