Corradi Hazel R, Chitapi Itai, Sewell B Trevor, Georgiadis Dimitris, Dive Vincent, Sturrock Edward D, Acharya K Ravi
Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom.
Biochemistry. 2007 May 8;46(18):5473-8. doi: 10.1021/bi700275e. Epub 2007 Apr 18.
Angiotensin I-converting enzyme (ACE) is central to the regulation of the renin-angiotensin system and is a key therapeutic target for combating hypertension and related cardiovascular diseases. Currently available drugs bind both active sites of its two homologous domains, although it is now understood that these domains function differently in vivo. The recently solved crystal structures of both domains (N and C) open the door to new domain-specific inhibitor design, taking advantage of the differences between these two large active sites. Here we present the first crystal structure at a resolution of 2.25 A of testis ACE (identical to the C domain of somatic ACE) with the highly C-domain-specific phosphinic inhibitor, RXPA380. Testis ACE retains the same conformation as seen in previously determined inhibitor complexes, but the RXPA380 central backbone conformation is more similar to that seen for the inhibitor captopril than enalaprilat. The RXPA380 molecule occupies more subsites of the testis ACE active site than the previously determined inhibitors and possesses bulky moieties that extend into the S2' and S2 subsites. Thus the high affinity of RXPA380 for the testis ACE/somatic ACE C domain is explained by the interaction of these bulky moieties with residues unique to these domains, specifically Phe 391, Val 379, and Val 380, that are not found in the N domain. The characterization of the extended active site and the binding of a potent C-domain-selective inhibitor provide the first structural data for the design of truly domain-specific pharmacophores.
血管紧张素I转换酶（ACE）是肾素-血管紧张素系统调节的核心，也是对抗高血压及相关心血管疾病的关键治疗靶点。目前可用的药物会结合其两个同源结构域的活性位点，尽管现在已经了解到这些结构域在体内的功能有所不同。最近解析得到的两个结构域（N和C）的晶体结构为基于结构差异设计新的结构域特异性抑制剂打开了大门。在此，我们展示了睾丸ACE（与体细胞ACE的C结构域相同）与高度C结构域特异性次膦酸抑制剂RXPA380形成的分辨率为2.25 Å的首个晶体结构。睾丸ACE保留了与先前确定的抑制剂复合物中相同的构象，但RXPA380的中心主链构象与抑制剂卡托普利的构象比依那普利拉的构象更为相似。RXPA380分子比先前确定的抑制剂占据了睾丸ACE活性位点更多的亚位点，并且拥有延伸到S2'和S2亚位点的庞大基团。因此，RXPA380对睾丸ACE/体细胞ACE C结构域的高亲和力可由这些庞大基团与这些结构域特有的残基（特别是苯丙氨酸391、缬氨酸379和缬氨酸380）之间的相互作用来解释，这些残基在N结构域中不存在。扩展活性位点的表征以及强效C结构域选择性抑制剂的结合为设计真正的结构域特异性药效基团提供了首个结构数据。
