Plasticity of S2-S4 specificity pockets of executioner caspase-7 revealed by structural and kinetic analysis
Plasticity of S2-S4 specificity pockets of executioner caspase-7 revealed by structural and kinetic analysis
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DOI：
10.1111/j.1742-4658.2007.05994.x
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发表时间：
2007-09-01
期刊：
影响因子：
5.4
通讯作者：
Weber, Irene T.
中科院分区：
文献类型：
--
作者：
Agniswamy, Johnson;Fang, Bin;Weber, Irene T.
与三个半胱天冬酶亚群的识别基序相比，许多半胱天冬酶的蛋白质底物在非规范位点被切割。为了深入了解caspase-7的特异性并帮助设计控制细胞死亡的药物，研究人员在六个肽类似物（Ac-DMQD-Cho、Ac-DQMD-Cho、ac - dld - cho、Ac-IEPD-Cho、Ac-ESMD-Cho、Ac-WEHD-Cho）的配合物中测定了caspase-7的晶体结构，这些复合物跨越了三个亚群的主要识别基元。晶体结构表明caspase-7的S2袋可以容纳多种残基。P3位置不需要Glu，因为具有不同P3残基的Ac-DMQD-Cho、Ac-DQMD-Cho和Ac-DNLD-Cho几乎与典型的Ac-DEVD-Cho一样有效。p4asp存在于较好的caspase-7抑制剂中。然而，刽子手caspase-7的S4口袋具有类似于引发者caspase-8的小分支脂肪或极性残基结合的交替区域。观察到的半胱天冬酶亚位的可塑性与报道的许多蛋白质在非规范位点的切割非常吻合。结果表明，P4-P1序列以外的因素，如外源，有助于半胱天冬酶在体内的底物特异性。在当前结构的分子表面发现的新的肽结合位点被认为是caspase-7的外源位点。这些结果应该考虑在设计选择性小分子抑制剂的药理学上重要的蛋白酶。
Many protein substrates of caspases are cleaved at noncanonical sites in comparison to the recognition motifs reported for the three caspase subgroups. To provide insight into the specificity and aid in the design of drugs to control cell death, crystal structures of caspase-7 were determined in complexes with six peptide analogs (Ac-DMQD-Cho, Ac-DQMD-Cho, Ac-DNLD-Cho, Ac-IEPD-Cho, Ac-ESMD-Cho, Ac-WEHD-Cho) that span the major recognition motifs of the three subgroups. The crystal structures show that the S2 pocket of caspase-7 can accommodate diverse residues. Glu is not required at the P3 position because Ac-DMQD-Cho, Ac-DQMD-Cho and Ac-DNLD-Cho with varied P3 residues are almost as potent as the canonical Ac-DEVD-Cho. P4 Asp was present in the better inhibitors of caspase-7. However, the S4 pocket of executioner caspase-7 has alternate regions for binding of small branched aliphatic or polar residues similar to those of initiator caspase-8. The observed plasticity of the caspase subsites agrees very well with the reported cleavage of many proteins at noncanonical sites. The results imply that factors other than the P4-P1 sequence, such as exosites, contribute to the in vivo substrate specificity of caspases. The novel peptide binding site identified on the molecular surface of the current structures is suggested to be an exosite of caspase-7. These results should be considered in the design of selective small molecule inhibitors of this pharmacologically important protease.