AMPylation is a posttranslational modification that generally modifies amino acid side chains of proteins with adenosine monophosphate (AMP)^1,2. Here we report that with ATP as the ligand and actin as the host activator, the effector protein LnaB of Legionella pneumophila exhibits AMPylase activity toward the phosphoryl group of phosphoribose on PR^R42-Ub that is generated by the SidE family effectors and deubiquitinases DupA/B in an E1/E2-independent ubiquitination process^3-7. The product of LnaB is further hydrolyzed by an ADP-ribosyl hydrolase, MavL, to be Ub, thereby preventing accumulation of PR^R42-Ub and ADPR^R42-Ub and protecting the canonical ubiquitination in host cells. LnaB represents a large family of AMPylases adopting a common structural fold, which is distinct from those of the previously known AMPylases, in bacterial pathogens of more than 20 species. Moreover, LnaB also exhibits robust phosphoryl AMPylase activity toward phosphorylated residues and produces unique ADPylation modification in proteins. During infection, LnaB AMPylates the conserved phosphorylated tyrosine residues in the activation loop of the Src family kinases^8,9, which dampens the host downstream phosphorylation signaling. Structural studies revealed the actin-dependent activation and catalytic mechanisms of the LnaB family of AMPylases. This study presents an unprecedented regulation and molecular mechanism in bacterial pathogenesis and protein phosphorylation.

AMPylation 是一种翻译后修饰，通常用单磷酸腺苷 (AMP) ^1,2 修饰蛋白质的氨基酸侧链。在此，我们报道以 ATP 为配体，肌动蛋白为宿主激活剂，嗜肺军团菌的效应蛋白 LnaB 对 SidE 家族产生的 PR ^R42 -Ub 上的磷酸核糖磷酰基表现出 AMPylase 活性不依赖 E1/E2 的泛素化过程中的效应子和去泛素化酶 DupA/B ^3-7 。 LnaB 的产物进一步被 ADP-核糖基水解酶 MavL 水解为 Ub，从而防止 PR ^R42 -Ub 和 ADPR ^R42 -Ub 的积累，保护经典泛素化在宿主细胞中。 LnaB 代表了一个大的 AMPylase 家族，其在 20 多个物种的细菌病原体中采用共同的结构折叠，与之前已知的 AMPylase 不同。此外，LnaB 还对磷酸化残基表现出强大的磷酸 AMPylase 活性，并在蛋白质中产生独特的 ADPylation 修饰。在感染过程中，LnaB AMPylate Src 家族激酶 ^8,9 激活环中保守的磷酸化酪氨酸残基，从而抑制宿主下游磷酸化信号传导。结构研究揭示了 AMPylase 的 LnaB 家族的肌动蛋白依赖性激活和催化机制。这项研究提出了细菌发病机制和蛋白质磷酸化方面前所未有的调控和分子机制。