Metabolite sensing signal processors in eukaryotic photosynthetic microorganisms: from molecular mechanisms to cellular functions

微生物的能力高度进化，能够调节不同的细胞功能，以应对环境的波动，如物理化学或营养变化(Silva-Rocha&de Lorenzo，2010)。虽然这些系统在特异性和复杂性方面有很大的差异，但一些传感信号处理器在生命的不同领域中是保守的。例子包括分支通路中的信号整合或串扰抑制(由Goulian，2010年审查)以及通过细菌、古生菌和植物中存在的PII家族蛋白进行的调控(Chellamuthu等人，2013年；Ermilova等人，2013年)。尽管原核和真核PII蛋白之间有高度的相似性，但我们可以揭示植物PII蛋白的一个根本新的性质：它们通过一个新的低亲和力谷氨酰胺结合位点来感知谷氨酰胺(Chellamuthu等人，2014)。除了已发表的结果，我们通过下拉分析发现，光合作用微生物中的PII细胞靶标显然比之前预期的要多得多。总而言之，这些结果表明，到目前为止，我们只研究了PII细胞功能的冰山一角。该项目的基本思想是，PII蛋白是氧气光合作用(微生物)生物体中关键的代谢物感测信号处理器。在这个项目中，来自圣彼得堡的研究小组将专注于定义PII介导的绿藻调控网络的生理意义。这些电路在藻类生理学中的意义及其在藻类生物技术应用中的影响将被讨论。在Tübingen，PII相互作用的分子生物学，从精氨酸合成的控制酶N-乙酰谷氨酸激酶的未解决的结构-功能方面，到新的PII控制的中央代谢酶的特征，将是研究的中心。

Microorganisms are highly evolved in their abilities to regulate distinct sets of cellular functions in response to fluctuations in the environment, such as physicochemical or nutritional changes (Silva-Rocha & de Lorenzo, 2010). Although these systems are highly diverse with respect to specificity and complexity, some sensing signal processors are conserved in the different domains of life. Examples include aspects of signal integration in branched pathways or cross-talk suppression (reviewed by Goulian, 2010) as well as regulation via proteins of the PII family that are present in bacteria, archaea and plants (Chellamuthu et al., 2013; Ermilova et al., 2013). Despite the high degree of similarity between prokaryotic and eukaryotic PII proteins, we could reveal a fundamentally novel property in plant PII proteins: they sense glutamine through a novel low affinity glutamine-binding site (Chellamuthu et al., 2014). In addition to the published results, we found by pull-down analysis, that there are apparently many more PII cellular targets in photosynthetic microorganisms than previously anticipated. Together, these results indicate that we have so far only studied a tip of an iceberg of the cellular functions of PII. The basic idea of the project is, that PII proteins are pivotal metabolite sensing signal processors in oxygenic photosynthetic (micro)organisms. In this project, the group from St. Petersburg will focus on the definition of physiological implications of PII-mediated regulatory networks in green algae. The significance of these circuits in algal physiology and its impact in algal biotechnological use will be addressed. In Tübingen, the molecular biology of PIi interactions, from unsolved structure-function aspects of the controlling enzyme of Arginien synthesis, N-acetyl-glutamate kinase, to the characterization of novel PII controlled enzymes of central metabolism, will be in the centre of research.