Structural basis for the activation of human procaspase-7
Structural basis for the activation of human procaspase-7
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DOI：
10.1073/pnas.221580098
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发表时间：
2001-12-18
影响因子：
11.1
通讯作者：
Bode, W
中科院分区：
文献类型：
--
作者：
Riedl, SJ;Fuentes-Prior, P;Bode, W
半胱天冬酶形成细胞凋亡的起始和执行阶段所需的蛋白酶家族。不同的促凋亡刺激导致起始剂半胱天冬酶-8和-9的激活，其进而通过蛋白水解切割激活共同的执行剂半胱天冬酶-3和-7。尽管已经报道了几种活性半胱天冬酶的晶体结构，但迄今为止还没有未切割的半胱天冬酶酶原的三维结构。我们测定了重组人C285 A半胱氨酸天冬氨酸蛋白酶原-7的2.9埃晶体结构，并阐明了半胱氨酸天冬氨酸蛋白酶的激活机制。同二聚体半胱天冬酶原-7的总体折叠类似于活性四聚体半胱天冬酶-7的折叠。每个单体被组织成两个结构化的亚结构域，由部分柔性的连接体连接，不对称地占据并阻断中心腔，这是活性半胱天冬酶的典型特征。这种阻断与功能性底物结合位点/活性位点不相容。在柔性接头内的蛋白水解裂解后，新形成的链末端离开空腔并向外折叠以形成稳定的结构。这些构象变化与完整活性位点裂缝的形成有关。因此，这种机制代表了一种以前未知类型的蛋白酶酶原激活。
Caspases form a family of proteinases required for the initiation and execution phases of apoptosis. Distinct proapoptotic stimuli lead to activation of the initiator caspases-8 and -9, which in turn activate the common executioner caspases-3 and -7 by proteolytic cleavage. Whereas crystal structures of several active caspases have been reported, no three-dimensional structure of an uncleaved caspase zymogen is available so far. We have determined the 2.9-Angstrom crystal structure of recombinant human C285A procaspase-7 and have elucidated the activation mechanism of caspases. The overall fold of the homodimeric procaspase-7 resembles that of the active tetrameric caspase-7. Each monomer is organized in two structured subdomains connected by partially flexible linkers, which asymmetrically occupy and block the central cavity, a typical feature of active caspases. This blockage is incompatible with a functional substrate binding site/active site. After proteolytic cleavage within the flexible linkers, the newly formed chain termini leave the cavity and fold outward to form stable structures. These conformational changes are associated with the formation of an intact active-site cleft. Therefore, this mechanism represents a formerly unknown type of proteinase zymogen activation.