Department of Chemistry and Biochemistry , Boise State University , 1910 University Dr. , Boise , Idaho 83725 , United States.
Department of Biological Chemistry and Molecular Pharmacology , Harvard Medical School , 240 Longwood Ave , Boston , Massachusetts 02115 , United States.
ACS Chem Biol. 2019 Oct 18;14(10):2305-2314. doi: 10.1021/acschembio.9b00671. Epub 2019 Oct 9.
Virulence in the Gram-negative pathogen relies in part on the efficient functioning of two LuxI/R dependent quorum sensing (QS) cascades, namely, the LasI/R and RhlI/R systems that generate and respond to (3-oxo)-dodecanoyl-l-homoserine lactone and butyryl-l-homoserine lactone, respectively. The two acyl homoserine lactone (AHL) synthases, LasI and RhlI, use 3-oxododecanoyl-ACP and butyryl-ACP, respectively, as the acyl-substrates to generate the corresponding autoinducer signals for the bacterium. Although AHL synthases represent excellent targets for developing QS modulators in , and in other related bacteria, the identification of potent and signal synthase specific inhibitors has represented a significant technical challenge. In the current study, we sought to test the utility of AHL analogs as potential modulators of an AHL synthase and selected RhlI in as an initial target. We systematically varied the chemical functionalities of the AHL headgroup, acyl chain tail, and head-to-tail linkage to construct a small library of signal analogs and evaluated them for RhlI modulatory activity. Although the native butyryl-l-homoserine lactone did not inhibit RhlI, we discovered that several of our long-chain, unsubstituted acyl-d-homoserine lactones and acyl-d-homocysteine thiolactones inhibited while a few of the 3-oxoacyl-chain counterparts activated the enzyme. Additional mechanistic investigations with acyl-substrate analogs and docking experiments with AHL analogs revealed two distinct inhibitor and activator binding pockets in the enzyme. This study provides the first evidence of the yet untapped potential of AHL analogs as signal synthase modulators of QS pathways.
革兰氏阴性病原体的毒力部分依赖于两种 LuxI/R 依赖性群体感应 (QS) 级联的有效作用，即 LasI/R 和 RhlI/R 系统，它们分别产生和响应 (3-氧代) -十二烷酰基-l-高丝氨酸内酯和丁酰基-l-高丝氨酸内酯。两种酰基高丝氨酸内酯 (AHL) 合酶 LasI 和 RhlI 分别使用 3-氧代十二烷酰基-ACP 和丁酰基-ACP 作为酰基底物，为细菌生成相应的自体诱导物信号。尽管 AHL 合酶是开发 QS 调节剂的极好靶点，但在 和其他相关细菌中，鉴定有效且信号特异性的抑制剂一直是一个重大技术挑战。在本研究中，我们试图测试 AHL 类似物作为潜在 AHL 合酶调节剂的效用，并选择 中的 RhlI 作为初始靶标。我们系统地改变 AHL 头基、酰基链尾和头尾连接的化学官能团，构建了一个小的信号类似物文库，并评估了它们对 RhlI 调节活性的影响。尽管天然的丁酰基-l-高丝氨酸内酯不能抑制 RhlI，但我们发现我们的几种长链、未取代的酰基-d-高丝氨酸内酯和酰基-d-高丝氨酸内酯硫内酯抑制了该酶，而一些 3-氧代酰基链对应物则激活了该酶。与酰基底物类似物的额外机制研究和 AHL 类似物的对接实验揭示了该酶中存在两个不同的抑制剂和激活剂结合口袋。这项研究首次提供了证据，证明 AHL 类似物作为 QS 途径信号合酶调节剂具有尚未开发的潜力。
