Mantovani Oliver, Haffner Michael, Selim Khaled A, Hagemann Martin, Forchhammer Karl
Institute of Biosciences, Department of Plant Physiology, University of Rostock, D-18059 Rostock, Germany.
Interfaculty Institute of Microbiology and Infection Medicine, Organismic Interactions Department, Cluster of Excellence 'Controlling Microbes to Fight Infections', Tübingen University, D-72076 Tübingen, Germany.
Microlife. 2023 Feb 23;4:uqad008. doi: 10.1093/femsml/uqad008. eCollection 2023.
Second messengers are a fundamental category of small molecules and ions that are involved in the regulation of many processes in all domains of life. Here we focus on cyanobacteria, prokaryotes playing important roles as primary producers in the geochemical cycles due to their capability of oxygenic photosynthesis and carbon and nitrogen fixation. Of particular interest is the inorganic carbon-concentrating mechanism (CCM), which allows cyanobacteria to concentrate CO near RubisCO. This mechanism needs to acclimate toward fluctuating conditions, such as inorganic carbon availability, intracellular energy levels, diurnal light cycle, light intensity, nitrogen availability, and redox state of the cell. During acclimation to such changing conditions, second messengers play a crucial role, particularly important is their interaction with the carbon control protein SbtB, a member of the PII regulator protein superfamily. SbtB is capable of binding several second messengers, uniquely adenyl nucleotides, to interact with different partners in a variety of responses. The main identified interaction partner is the bicarbonate transporter SbtA, which is regulated via SbtB depending on the energy state of the cell, the light conditions, and different CO availability, including cAMP signaling. The interaction with the glycogen branching enzyme, GlgB, showed a role for SbtB in the c-di-AMP-dependent regulation of glycogen synthesis during the diurnal life cycle of cyanobacteria. SbtB has also been shown to impact gene expression and metabolism during acclimation to changing CO conditions. This review summarizes the current knowledge about the complex second messenger regulatory network in cyanobacteria, with emphasis on carbon metabolism.
第二信使是一类基本的小分子和离子，参与生命所有领域中许多过程的调节。在此，我们聚焦于蓝细菌，这类原核生物由于其进行有氧光合作用以及固定碳和氮的能力，在地球化学循环中作为初级生产者发挥着重要作用。特别令人感兴趣的是无机碳浓缩机制（CCM），它使蓝细菌能够在核酮糖-1,5-二磷酸羧化酶/加氧酶（RubisCO）附近浓缩二氧化碳。这种机制需要适应波动的条件，如无机碳的可利用性、细胞内能量水平、昼夜光周期、光照强度、氮的可利用性以及细胞的氧化还原状态。在适应这些变化的条件过程中，第二信使发挥着关键作用，尤其重要的是它们与碳控制蛋白SbtB的相互作用，SbtB是PII调节蛋白超家族的成员。SbtB能够结合多种第二信使，特别是腺苷酸核苷酸，以在各种反应中与不同的伙伴相互作用。主要确定的相互作用伙伴是碳酸氢盐转运蛋白SbtA，它通过SbtB根据细胞的能量状态、光照条件以及包括环磷酸腺苷（cAMP）信号在内的不同二氧化碳可利用性进行调节。与糖原分支酶GlgB的相互作用表明，SbtB在蓝细菌昼夜生命周期中依赖环二腺苷酸（c-di-AMP）调节糖原合成的过程中发挥作用。研究还表明，SbtB在适应不断变化的二氧化碳条件过程中会影响基因表达和新陈代谢。本综述总结了目前关于蓝细菌中复杂的第二信使调节网络的知识，重点是碳代谢。
