The murine orthologue of human antichymotrypsin - A structural paradigm for CLADE A3 serpins
The murine orthologue of human antichymotrypsin - A structural paradigm for CLADE A3 serpins
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DOI：
10.1074/jbc.m505598200
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发表时间：
2005-12-30
影响因子：
4.8
通讯作者：
Whisstock, JC
中科院分区：
文献类型：
--
作者：
Horvath, AJ;Irving, JA;Whisstock, JC
抗胰凝乳蛋白酶（SERPINA 3）是丝氨酸蛋白酶抑制剂超家族的广泛表达的成员，是调节炎症反应期间释放的白细胞蛋白酶所需的，并且在淀粉样脑病的发展中具有允许的作用。尽管其生物学意义，目前还没有可用的结构，这种丝氨酸蛋白酶抑制剂在其天然的，抑制状态。我们在这里提出了第一个完全完善的结构，鼠抗胰凝乳蛋白酶直向同源物2.1埃，我们建议作为模板的其他抗胰凝乳蛋白酶样丝氨酸蛋白酶抑制剂。鼠丝氨酸蛋白酶抑制剂3 n的结构的一个最意想不到的特征是，它揭示了反应中心环（RCL）被部分插入A β-片层中，A β-片层是与其他丝氨酸蛋白酶抑制剂中的配体依赖性激活相关的结构基序。此外，RCL通过盐桥稳定，并且其平面与抗胰蛋白酶的RCL成90 °取向。该丝氨酸蛋白酶抑制剂的生物化学和生物物理分析表明，它是人白细胞弹性蛋白酶（k（a）：4 +/- 0.9 x 10（6）M-1 s（-1））和组织蛋白酶G（ka：7.9 +/- 0.9 x 10（5）M-1 s（-1））的快速有效抑制剂，其活性范围介于人抗胰凝乳蛋白酶和人抗胰蛋白酶之间。进化分析表明，在丝氨酸蛋白酶抑制剂超家族的这个亚分支（A3）中，经历正选择并对序列多样性有贡献的残基基本上限于RCL的P-4 - P-6'区、远端铰链和链4 B和5 B之间的环。
Antichymotrypsin (SERPINA3) is a widely expressed member of the serpin superfamily, required for the regulation of leukocyte proteases released during an inflammatory response and with a permissive role in the development of amyloid encephalopathy. Despite its biological significance, there is at present no available structure of this serpin in its native, inhibitory state. We present here the first fully refined structure of a murine antichymotrypsin orthologue to 2.1 angstrom, which we propose as a template for other antichymotrypsin-like serpins. A most unexpected feature of the structure of murine serpina3n is that it reveals the reactive center loop (RCL) to be partially inserted into the A beta-sheet, a structural motif associated with ligand-dependent activation in other serpins. The RCL is, in addition, stabilized by salt bridges, and its plane is oriented at 90 to the RCL of antitrypsin. A biochemical and biophysical analysis of this serpin demonstrates that it is a fast and efficient inhibitor of human leukocyte elastase (k(a):4 +/- 0.9 x 10(6) M-1 s(-1)) and cathepsin G (ka: 7.9 +/- 0.9 x 10(5) M-1 s(-1)) giving a spectrum of activity intermediate between that of human antichymotrypsin and human antitrypsin. An evolutionary analysis reveals that residues subject to positive selection and that have contributed to the diversity of sequences in this sub-branch (A3) of the serpin superfamily are essentially restricted to the P-4 - P-6' region of the RCL, the distal hinge, and the loop between strands 4B and 5B.