Mpakali Anastasia, Saridakis Emmanuel, Giastas Petros, Maben Zachary, Stern Lawrence J, Larhed Mats, Hallberg Mathias, Stratikos Efstratios
National Center for Scientific Research Demokritos, Agia Paraskevi, Athens 15341, Greece.
Department of Pathology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, United States.
ACS Med Chem Lett. 2020 Jun 2;11(7):1429-1434. doi: 10.1021/acsmedchemlett.0c00172. eCollection 2020 Jul 9.
Insulin-regulated aminopeptidase (IRAP) is a transmembrane zinc metallopeptidase with many important biological functions and an emerging pharmacological target. Although previous structural studies have given insight on how IRAP recognizes linear peptides, how it recognizes its physiological cyclic ligands remains elusive. Here, we report the first crystal structure of IRAP with the macrocyclic peptide inhibitor HA08 that combines structural elements from angiotensin IV and the physiological substrates oxytocin and vasopressin. The compound is found in the catalytic site in a near canonical substrate-like configuration and inhibits by a competitive mechanism. Comparison with previously solved structures of IRAP along with small-angle X-ray scattering experiments suggests that IRAP is in an open conformation in solution but undergoes a closing conformational change upon inhibitor binding. Stabilization of the closed conformation in combination with catalytic water exclusion by the tightly juxtaposed GAMEN loop is proposed as a mechanism of inhibition.
胰岛素调节氨肽酶（IRAP）是一种具有多种重要生物学功能的跨膜锌金属肽酶，也是一个新兴的药理学靶点。尽管先前的结构研究已经揭示了IRAP如何识别线性肽，但其如何识别其生理环状配体仍不清楚。在此，我们报道了IRAP与大环肽抑制剂HA08的首个晶体结构，HA08结合了血管紧张素IV以及生理底物催产素和加压素的结构元件。该化合物以接近典型底物样的构象存在于催化位点，并通过竞争性机制发挥抑制作用。将其与先前解析的IRAP结构进行比较以及小角X射线散射实验表明，IRAP在溶液中处于开放构象，但在抑制剂结合后会发生构象闭合变化。紧密相邻的GAMEN环结合催化水的排除从而稳定闭合构象，被认为是一种抑制机制。
