College of Life Sciences, Northwest University, Xi'an, ShaanXi, China.
College of Medicine, Southern University of Science and Technology, Shenzhen, China.
Nat Commun. 2024 Feb 29;15(1):1860. doi: 10.1038/s41467-024-46149-3.
Cyclic dimeric guanosine monophosphate (c-di-GMP) serves as a bacterial second messenger that modulates various processes including biofilm formation, motility, and host-microbe symbiosis. Numerous studies have conducted comprehensive analysis of c-di-GMP. However, the mechanisms by which certain environmental signals such as iron control intracellular c-di-GMP levels are unclear. Here, we show that iron regulates c-di-GMP levels in Pseudomonas aeruginosa by modulating the interaction between an iron-sensing protein, IsmP, and a diguanylate cyclase, ImcA. Binding of iron to the CHASE4 domain of IsmP inhibits the IsmP-ImcA interaction, which leads to increased c-di-GMP synthesis by ImcA, thus promoting biofilm formation and reducing bacterial motility. Structural characterization of the apo-CHASE4 domain and its binding to iron allows us to pinpoint residues defining its specificity. In addition, the cryo-electron microscopy structure of ImcA in complex with a c-di-GMP analog (GMPCPP) suggests a unique conformation in which the compound binds to the catalytic pockets and to the membrane-proximal side located at the cytoplasm. Thus, our results indicate that a CHASE4 domain directly senses iron and modulates the crosstalk between c-di-GMP metabolic enzymes.
环状二鸟苷酸（cyclic dimeric guanosine monophosphate，c-di-GMP）作为细菌的第二信使，调节包括生物膜形成、运动性和宿主微生物共生在内的各种过程。大量研究对 c-di-GMP 进行了全面分析。然而，某些环境信号（如铁）控制细胞内 c-di-GMP 水平的机制尚不清楚。在这里，我们表明，铁通过调节铁感应蛋白 IsmP 和双鸟苷酸环化酶 ImcA 之间的相互作用来调节铜绿假单胞菌中的 c-di-GMP 水平。铁与 IsmP 的 CHASE4 结构域结合抑制了 IsmP-ImcA 相互作用，导致 ImcA 合成 c-di-GMP 增加，从而促进生物膜形成并降低细菌运动性。apo-CHASE4 结构域及其与铁结合的结构特征使我们能够确定定义其特异性的残基。此外，与 c-di-GMP 类似物（GMPCPP）复合物的 ImcA 的冷冻电镜结构表明了一种独特的构象，其中该化合物结合到催化口袋和位于细胞质侧的膜近端侧。因此，我们的结果表明，CHASE4 结构域直接感应铁并调节 c-di-GMP 代谢酶之间的串扰。
