Structural insights into SUN-KASH complexes across the nuclear envelope
Structural insights into SUN-KASH complexes across the nuclear envelope
复制标题
跨核膜的 SUN-KASH 复合物的结构见解
DOI：
10.1038/cr.2012.126
复制
发表时间：
2012-10-01
期刊：
影响因子：
44.1
通讯作者：
Zhou, Zhaocai
中科院分区：
文献类型：
--
作者：
Wang, Wenjia;Shi, Zhubing;Zhou, Zhaocai
核骨架连接子和细胞骨架(LINC)复合体由含有SUN和KASH结构域的蛋白质组成，连接核膜的内膜和外膜。LINC复合体在核定位、细胞极化和细胞刚性等方面发挥着重要作用。此前，我们报道了人类SUN2的同源三聚体结构。我们现在已经确定了人类SUN2-Kash络合物的晶体结构。在复杂的结构中，SUN结构域的同源三聚体与三个独立的钩状Kash多肽结合。复合体中太阳结构域的整体构象与太阳结构域的脱脂状态非常相似。一个主要的构象变化涉及Kash结合的SUN结构域的AA‘环，它重新排列形成与Kash肽相互作用的小β-折叠。Kash结构域的PPPT基序紧密地装配在SUN结构域的均三聚体界面上的疏水口袋中，我们称之为BI-Pocket。此外，太阳域高三聚体的两个相邻原型通过疏水相互作用和氢键夹住了Kash结构域。在体外，这些结合位点的突变会破坏或减少SUN和Kash结构域之间的联系。此外，野生型而不是突变型的SUN2可促进Ovcar-3细胞的迁移。这些结果提供了LINC复合体的结构模型，这对于进一步研究细胞质和核质之间的物理和功能耦合是必不可少的。
Linker of the nucleoskeleton and the cytoskeleton (LINC) complexes are composed of SUN and KASH domain-containing proteins and bridge the inner and outer membranes of the nuclear envelope. LINC complexes play critical roles in nuclear positioning, cell polarization and cellular stiffness. Previously, we reported the homotrimeric structure of human SUN2. We have now determined the crystal structure of the human SUN2-KASH complex. In the complex structure, the SUN domain homotrimer binds to three independent “hook”-like KASH peptides. The overall conformation of the SUN domain in the complex closely resembles the SUN domain in its apo state. A major conformational change involves the AA'-loop of KASH-bound SUN domain, which rearranges to form a mini β-sheet that interacts with the KASH peptide. The PPPT motif of the KASH domain fits tightly into a hydrophobic pocket on the homotrimeric interface of the SUN domain, which we termed the BI-pocket. Moreover, two adjacent protomers of the SUN domain homotrimer sandwich the KASH domain by hydrophobic interaction and hydrogen bonding. Mutations of these binding sites disrupt or reduce the association between the SUN and KASH domains in vitro. In addition, transfection of wild-type, but not mutant, SUN2 promotes cell migration in Ovcar-3 cells. These results provide a structural model of the LINC complex, which is essential for additional study of the physical and functional coupling between the cytoplasm and the nucleoplasm.