Challenging the role of plastid cotranslational N-terminal modifications upon stress response

叶绿体的主要功能是作为生物反应器将光转化为化学能。此外，它们还作为细胞内通讯和介导环境影响的调节枢纽来调节核基因的表达。叶绿体蛋白由质体或核基因组编码。一些叶绿体多蛋白复合物，如RuBisCO （d-核酮糖1,5-二磷酸羧化酶/加氧酶），是卡尔文-本森循环的主要酶，也是地球上最丰富的蛋白质，是由质体和核编码的蛋白质亚基组装而成的。所有核和质体编码的叶绿体定位蛋白都经历了许多共和翻译后修饰（CTMs和PTMs），这些修饰在控制这些蛋白的稳定性、积累、活性、组装和区隔化中起着重要作用。然而，迄今为止，对质体蛋白及其催化修饰剂的CTMs和PTMs的研究还不够深入，修饰的数量在不断增加。在过去的几年里，三个团队（Gif, m<s:2> nster和Berlin）的合作工作带来了多个初步结果，突出了质体n端修饰剂的独特性质以及催化npm的特定和基本调节功能，这些结果现在建立了CANMORE项目的研究假设和目标。CANMORE的总体目标是阐明特定质体n端修饰（npm）的作用及其与其他ppm的调节相互依赖性。通过三个相互关联的目标，我们将对npm和相关ptm中涉及的质体修饰剂进行结构和机制表征。重点将给予RuBisCO大亚基的非常规和神秘的n端成熟。因此，详细了解RuBisCO上发生的蛋白质修饰，特别是在不利环境条件下发生的蛋白质修饰，对于我们理解和可能的未来改进RuBisCO活性和光合作用是必要的。在这种情况下，我们将提供一个对温度胁迫的反应的质体n端和乙酰基的全面研究，这对RuBisCO活性特别重要。总的来说，CANMORE项目不仅将提供对质体NPM机制的全面分析，而且还将大大提高我们对NPM对特定质体活动和不断变化的环境条件的影响的理解。在这个项目中，将提出蛋白质组学、生物化学、结构生物学、遗传学和细胞生物学等互补方法的协同作用。CANMORE项目将汇集三个高度互补的团队[Carmela Giglione， Team1（法国）；伯恩哈德·格林，第二队（德国）；和Iris Finkemeier， Team3,（德国）]，在CTMs/PTMs和叶绿体生理学方面都有兴趣并处于世界领先地位。

Chloroplasts primarily function as bioreactors converting light into chemical energy. In addition, they also act as regulatory hub for intracellular communication and mediation of environmental impacts to regulate nuclear gene expression. Chloroplast proteins are encoded either by the plastid or nuclear genome. Several chloroplast multi-protein complexes, such as RuBisCO (D-ribulose 1,5-bisphosphate carboxylase/oxygenase), which is the major enzyme of the Calvin-Benson cycle and the most abundant protein on earth, are assembled from plastid- as well as nuclear-encoded protein subunits. All nuclear and plastid-encoded chloroplast-localized proteins undergo many co- and post-translational modifications (CTMs and PTMs), which have important roles in controlling stability, accumulation, activity, assembly, and compartmentalisation of these proteins. However, CTMs and PTMs of plastid proteins and their catalytic modifiers have not intensively been explored up to date and the number of modifications continuously increases. Over the last years, the collaborative work among the three teams (Gif, Münster and Berlin) have brought multiple preliminary results highlighting unique properties of plastid N-terminal modifiers together with specific and essential modulated functions of the catalysed NPMs, which now build the research hypothesis and objectives of the CANMORE project. The overarching aim of CANMORE is to elucidate the role(s) of specific plastid N-terminal modifications (NPMs) and their regulatory interdependency with other PTMs. Via three interconnecting objectives, we will perform a structural and mechanistic characterization of the plastid modifiers involved in NPMs and related PTMs. Strong emphasis will be given to the unconventional and enigmatic N-terminal maturation of the RuBisCO large subunit. Hence, a detailed understanding of the protein modifications occurring on RuBisCO, especially under adverse environmental conditions, will be necessary for our understanding and possible future improvement of RuBisCO activity and photosynthesis in general. In this context, we will provide a thorough investigation of the plastid N-terminome and acetylome in response to temperature stress, which is particularly important for RuBisCO activity. Collectively, the CANMORE project will not only provide a comprehensive analysis of the plastid NPM machinery, but will also significantly enhance our understanding of the consequences of NPMs on specific plastid activities and during changing environmental conditions. For this project, a synergy of complementary approaches involving proteomics, biochemistry, structural biology, genetics and cell biology will be proposed. The CANMORE project will bring together three highly complementary groups [Carmela Giglione, Team1 (France); Bernhard Grimm, Team2 (Germany); and Iris Finkemeier, Team3, (Germany)] with interests and world lead in both CTMs/PTMs and chloroplast physiology.