Provincial University Key Laboratory of Cellular Stress Response and Metabolic Regulation, The Key Laboratory of Innate Immune Biology of Fujian Province, Biomedical Research Center of South China, Key Laboratory of OptoElectronic Science and Technology for Medicine of the Ministry of Education, College of Life Sciences, Fujian Normal University, Fuzhou, China.
Department of Neurology, Fujian Medical University Union Hospital, Fuzhou, China.
J Biol Chem. 2022 Oct;298(10):102414. doi: 10.1016/j.jbc.2022.102414. Epub 2022 Aug 22.
Legionella pneumophila, a bacterial pathogen that causes a severe pneumonia known as Legionnaires' disease, extensively exploits the ubiquitin (Ub) pathway in the infected host cells through certain virulence effectors excreted by the Dot/Icm system. To date, several Dot/Icm effectors have been found to act as Ub ligases, and four effectors, including LotA, LotB, LotC, and Ceg7, have been identified as deubiquitinases (DUBs) from the ovarian tumor (OTU) domain family. LotA is unique among other OTU DUBs because it possesses two distinct DUB domains and exclusively exhibits catalytic activity against K6-linked diUb and polyUb chains. However, the structure of LotA and the molecular mechanism for the dual DUB activity remains elusive. In this study, we solved the structure of LotA in complex with proximally bound Ub and distal covalently bound Ub. Both Ub molecules are bound to the DUB1 domain and mimic a K6-linked diUb. Structural analysis reveals that the DUB1 domain utilizes a distinct mechanism for recognition of the K6-linked diUb within a large S1' binding site that is uncommon to OTU DUBs. Structural fold of the LotA DUB2 domain closely resembles LotB and LotC, similarly containing an extra α-helix lobe that has been demonstrated to play an important role in Ub binding. Collectively, our study uncovers the structural basis for the dual catalytic activity of the unique OTU family DUB LotA.
嗜肺军团菌是一种细菌病原体，可引起严重肺炎，称为军团病，通过 Dot/Icm 系统分泌的某些毒力效应物，在感染的宿主细胞中广泛利用泛素 (Ub) 途径。迄今为止，已经发现几种 Dot/Icm 效应物可作为 Ub 连接酶，并且包括 LotA、LotB、LotC 和 Ceg7 在内的四个效应物已被鉴定为来自卵巢肿瘤 (OTU) 结构域家族的去泛素化酶 (DUB)。LotA 在其他 OTU DUB 中是独一无二的，因为它具有两个独特的 DUB 结构域，并且仅对 K6 连接的二泛素和多泛素链表现出催化活性。然而，LotA 的结构和双 DUB 活性的分子机制仍然难以捉摸。在这项研究中，我们解决了与近端结合的 Ub 和远端共价结合的 Ub 复合的 LotA 结构。两个 Ub 分子都结合到 DUB1 结构域上，并模拟 K6 连接的二泛素。结构分析表明，DUB1 结构域利用一种独特的机制来识别大 S1'结合位点内的 K6 连接的二泛素，这在 OTU DUB 中并不常见。LotA DUB2 结构域的折叠结构与 LotB 和 LotC 非常相似，同样包含一个额外的α-螺旋叶，该叶已被证明在 Ub 结合中起重要作用。总的来说，我们的研究揭示了独特的 OTU 家族 DUB LotA 双催化活性的结构基础。
