Bacterial cyclic-di-GMP (c-di-GMP) production is associated with biofilm development and the switch from acute to chronic infections. In Pseudomonas aeruginosa, the diguanylate cyclase (DGC) SiaD and phosphatase SiaA, which are co-transcribed as part of a siaABCD operon, are essential for cellular aggregation. However, the detailed functions of this operon and the relationships among its constituent genes are unknown. Here, we demonstrate that the siaABCD operon encodes for a signaling network that regulates SiaD enzymatic activity to control biofilm and aggregates formation. Through protein-protein interaction, SiaC promotes SiaD diguanylate cyclase activity. Biochemical and structural data revealed that SiaB is an unusual protein kinase that phosphorylates SiaC, whereas SiaA phosphatase can dephosphorylate SiaC. The phosphorylation state of SiaC is critical for its interaction with SiaD, which will switch on or off the DGC activity of SiaD and regulate c-di-GMP levels and subsequent virulence phenotypes. Collectively, our data provide insights into the molecular mechanisms underlying the modulation of DGC activity associated with chronic infections, which may facilitate the development of antimicrobial drugs.

中文翻译：

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SiaA / B / C / D信号网络调节铜绿假单胞菌中的生物膜形成。

细菌性循环二GMP（c-di-GMP）的产生与生物膜的形成以及从急性感染向慢性感染的转变有关。在铜绿假单胞菌中，作为siaABCD操纵子的一部分共转录的双鸟苷酸环化酶（DGC）SiaD和磷酸酶SiaA是细胞聚集所必需的。但是，该操纵子的详细功能及其组成基因之间的关系尚不清楚。在这里，我们证明siaABCD操纵子编码一个信号网络，该网络调节SiaD酶活性以控制生物膜和聚集体的形成。通过蛋白质相互作用，SiaC可以促进SiaD双鸟苷酸环化酶的活性。生化和结构数据表明，SiaB是一种不寻常的蛋白激酶，可以使SiaC磷酸化，而SiaA磷酸酶可以使SiaC脱磷酸。SiaC的磷酸化状态对于其与SiaD的相互作用至关重要，这将开启或关闭SiaD的DGC活性并调节c-di-GMP水平和随后的毒力表型。总的来说，我们的数据提供了对与慢性感染相关的DGC活性调节的潜在分子机制的见解，这可能有助于开发抗菌药物。