Institute of Molecular Physiology (imP), Microbiology and Biotechnology, Johannes Gutenberg University, Biocenter II, Hanns-Dieter-Hüsch-Weg 17, 55128, Mainz, Germany.
BMC Microbiol. 2023 Aug 26;23(1):236. doi: 10.1186/s12866-023-02989-5.
Adenylate cyclases (ACs) generate the second messenger cyclic AMP (cAMP), which is found in all domains of life and is involved in the regulation of various cell physiological and metabolic processes. In the plant symbiotic bacterium Sinorhizobium meliloti, synthesis of cAMP by the membrane-bound AC CyaC responds to the redox state of the respiratory chain and the respiratory quinones. However, nothing is known about the signaling cascade that is initiated by cAMP produced by CyaC.
Here, the CRP-like transcriptional regulator Clr and the TetR-like regulator CycR (TR01819 protein) were identified to interact with CyaC using the bacterial two-hybrid system (BACTH), co-sedimentation assays, and surface plasmon resonance spectroscopy. Interaction of CycR with Clr, and of CyaC with Clr requires the presence of cAMP and of ATP, respectively, whereas that of CyaC with CycR was independent of the nucleotides.
The data implicate a ternary CyaC×CycR×cAMP-Clr complex, functioning as a specific signaling cascade which is formed after activation of CyaC and synthesis of cAMP. cAMP-Clr is thought to work in complex with CycR to regulate a subset of genes of the cAMP-Clr regulon in S. meliloti.
腺嘌呤核苷酸环化酶（ACs）生成第二信使环腺苷酸（cAMP），该物质存在于所有生命领域，参与调节各种细胞生理和代谢过程。在植物共生菌根瘤菌（Sinorhizobium meliloti）中，膜结合型 AC CyaC 合成 cAMP 响应呼吸链和呼吸醌的氧化还原状态。然而，关于 CyaC 产生的 cAMP 引发的信号级联反应还一无所知。
本研究利用细菌双杂交系统（BACTH）、共沉淀实验和表面等离子体共振光谱法，鉴定到 CRP 样转录调节因子 Clr 和 TetR 样调节因子 CycR（TR01819 蛋白）与 CyaC 相互作用。CycR 与 Clr 的相互作用，以及 CyaC 与 Clr 的相互作用均需要 cAMP 和 ATP 的存在，而 CyaC 与 CycR 的相互作用则不依赖于核苷酸。
这些数据表明存在一个 CyaC×CycR×cAMP-Clr 三元复合物，作为一个特定的信号级联反应，该反应在 CyaC 激活和 cAMP 合成后形成。cAMP-Clr 被认为与 CycR 形成复合物，以调节根瘤菌中 cAMP-Clr 调控子的一组特定基因。
