Molecular mechanism for the regulation of yeast separase by securin.
Molecular mechanism for the regulation of yeast separase by securin.
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DOI：
10.1038/nature21061
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发表时间：
2017-02-09
期刊：
影响因子：
64.8
通讯作者：
Tong L
中科院分区：
文献类型：
--
作者：
Luo S;Tong L
在染色体分离过程中，分离酶在解除姐妹染色单体间的凝聚力方面起着关键作用。Separase在人类肿瘤中过度表达，使其成为药物发现的潜在靶点。分离酶的蛋白酶活性受到抑制剂securin的严格调节，securin与分离酶形成紧密的复合物，并且还可以稳定该酶。分离酶是一种大酶，分子量为140-250 kD，N末端有一个α螺旋区，C末端有一个半胱天冬酶样催化结构域（CD）。虽然分离酶的C-末端两个结构域的晶体结构和分离酶-securin复合物的低分辨率电子显微镜重建已被报道，但全长分离酶的原子结构，特别是与securin的复合物尚不清楚。在这里，我们报告的晶体结构在高达2.6纳米分辨率的酵母酿酒酵母分离酶securin复合物。分离酶的α-螺旋区（也称为Esp 1）包含四个结构域（I-IV），在CD之前有一个底物结合结构域（SD），与CD紧密结合。securin（Pds 1）的残基258-373被称为分离酶相互作用片段（SIS），主要处于延伸构象，并贯穿分离酶的整个长度，与其所有结构域具有相互作用。最重要的是，securin的残基258-269位于分离酶活性位点，阐明了其抑制机制。生物化学研究证实了结构的观察，并指出，接触分离酶活性位点外的稳定复合物是至关重要的，从而定义了分离酶的螺旋区域的重要功能。
Separase has a critical role in dissolving the cohesion among sister chromatids during chromosome segregation . Separase is over-expressed in human tumors, making it a potential target for drug discovery . The protease activity of separase is strictly regulated by the inhibitor securin, which forms a tight complex with separase and may also stabilize this enzyme . Separases are large, 140–250 kD enzymes, with an N-terminal α-helical region and a caspase-like catalytic domain (CD) at the C-terminus. While crystal structures of the C-terminal two domains of separase and low-resolution electron microscopy reconstructions of the separase-securin complex have been reported, the atomic structures of full-length separase and especially the complex with securin are not known. Here we report crystal structures at up to 2.6 Å resolution of the yeast Saccharomyces cerevisiae separase-securin complex. The α-helical region of separase (also known as Esp1) contains four domains (I–IV), and a substrate-binding domain (SD) immediately precedes the CD and has tight associations with it. The separase-securin complex assumes a highly elongated structure. Residues 258–373 of securin (Pds1), named the separase interaction segment (SIS), is primarily in an extended conformation and traverses the entire length of separase, having interactions with all of its domains. Most importantly, residues 258–269 of securin are located in the separase active site, illuminating its mechanism of inhibition. Biochemical studies confirm the structural observations and indicate that contacts outside the separase active site are crucial for stabilizing the complex, thereby defining an important function for the helical region of separase.