Cryo-EM structure of a metazoan separase-securin complex at near-atomic resolution.
Cryo-EM structure of a metazoan separase-securin complex at near-atomic resolution.
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DOI：
10.1038/nsmb.3386
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发表时间：
2017-04
影响因子：
16.8
通讯作者：
Barford D
中科院分区：
文献类型：
--
作者：
Boland A;Martin TG;Zhang Z;Yang J;Bai XC;Chang L;Scheres SH;Barford D
分离酶是一种半胱天冬酶家族蛋白酶，通过切割粘附素的Kleisin亚基（Scc 1和Rec 8）启动染色单体分离，并通过切割kendrin和Slk 19调节中心体复制和有丝分裂纺锤体功能。为了了解securin调控分离酶的机制，我们使用单粒子冷冻电镜来确定C。线虫分离酶-安全蛋白复合物。Separase采用三角形双叶结构，包括N-末端类似于四肽重复（TPR）的α-螺线管结构域对接到保守的C-末端蛋白酶结构域。Securin从事分离酶在一个扩展的反平行构象相互作用的两个叶。它通过与催化位点通过伪底物机制相互作用来抑制分离酶，揭示了在被抑制的分离酶-securin复合物中，催化位点采用与底物结合相容的构象。Securin被保护免于切割，因为P1位置的脂肪族侧链通过破坏催化位点残基的组织来抑制蛋白酶活性。
Separase is a caspase-family protease that initiates chromatid segregation by cleaving the kleisin subunits (Scc1 and Rec8) of cohesin, and regulates centrosome duplication and mitotic spindle function through cleavage of kendrin and Slk19. To understand the mechanisms of separase regulation by securin we used single particle cryo-EM to determine a near-atomic resolution structure of the C. elegans separase-securin complex. Separase adopts a triangular-shaped bilobal architecture comprising an N-terminal tetratricopeptide repeat (TPR)-like α-solenoid domain docked onto the conserved C-terminal protease domain. Securin engages separase in an extended antiparallel conformation interacting with both lobes. It inhibits separase by interacting with the catalytic site through a pseudo-substrate mechanism, revealing that in the inhibited separase-securin complex, the catalytic site adopts a conformation compatible with substrate binding. Securin is protected from cleavage because an aliphatic side-chain at the P1 position represses protease activity by disrupting the organization of catalytic site residues.