Collaborative Research: Role of SCY2, a New Envelope Localized Translocase, in Plastid Biogenesis

智慧地球上的大部分能量最终来自太阳，而植物叶绿体是关键的细胞器，因为它们允许植物捕捉太阳能，并通过光合作用将这些能量转化为糖。大多数在叶绿体中执行这些重要任务的蛋白质都是在植物细胞的胞浆中合成的，被吸收到叶绿体基质隔室，然后必须通过转位酶特异性地靶向五个额外的叶绿体隔室之一，转位酶是一种将蛋白质运输到膜双层或进入膜双层的酶。关于这个复杂的蛋白质定位网络，一个中心悬而未决的问题是：什么系统(S)负责转位酶蛋白质的靶向和整合？最近发现了一种定位于叶绿体内膜的SEC转位酶。破坏这种转位酶的突变会导致死亡，这表明在叶绿体功能中起着至关重要的作用。初步结果表明，这个命名为Sec2的系统是主要的转位酶，负责将所有其他转位酶蛋白放置到正确的叶绿体间隔中。Sec2将通过这个项目得到进一步的描述。具体目标包括鉴定系统的所有组成部分，鉴定Sec2靶向和转位/整合的蛋白质，以及建立一个分析系统来研究这个转位系统对能量、辅助因子和靶向信息的需求。这项研究的成功完成将使人们更深入地了解这种新的转位酶在叶绿体生物发生中可能发挥的关键作用。他的项目将为本科生、研究生和研究生的年轻科学家提供遗传学和生物化学方面的交叉培训机会。项目人员还将通过指导本科生实践研究经验来学习宝贵的教学和指导技能。在这个项目中产生的植物品系将是有价值的研究工具，并将被分发给其他对叶绿体感兴趣的实验室。最后，由于许多重要的代谢和生物合成功能，包括光合作用和脂肪酸、必需氨基酸和维生素的合成，都集中在叶绿体中，这项工作可能会有实际应用，因为人们试图修改、优化或以其他方式控制这些能力。

INTELLECTUAL MERITMost of the energy on earth comes ultimately from the sun, and plant chloroplasts are critical cellular organelles because they allow plants to capture solar energy and convert this energy to sugars through the process of photosynthesis. Most of the proteins that perform these important tasks in chloroplasts are synthesized in the cytosol of the plant cell, are taken up into the chloroplast stromal compartment, and then have to be specifically targeted to one of five additional chloroplast compartments by translocases, enzymes that transport proteins across or into membrane bilayers. A central unanswered question regarding this intricate protein localization network is: What system(s) are responsible for targeting and integration of the translocase proteins? A Sec translocase was recently discovered that is localized to the inner envelope of the chloroplast. Mutations that disrupt this translocase result in death, suggesting a critically important role in chloroplast function. Preliminary results suggest that this system, designated Sec2, is the master translocase, responsible for the placement of all other translocase proteins into their correct chloroplast compartment. Sec2 will be further characterized through this project. Specific aims include identification of all the components of the system, characterization of the proteins targeted and translocated/integrated by Sec2, and the establishment of an assay system to investigate the requirements for energy, accessory factors, and targeting information for this translocase system. Successful completion of the research will result in increased insight into the pivotal role that this novel translocase may play in the biogenesis of the chloroplast. BROADER IMPACTSThis project will provide cross-training opportunities in genetics and biochemistry for young scientists at the undergraduate, graduate, and postgraduate level. Project personnel will also learn valuable teaching and mentoring skills by supervising undergraduate students in hands-on research experiences. The plant lines that will be generated in this project will be valuable research tools and will be distributed to other laboratories interested in chloroplasts. Finally, because many vital metabolic and biosynthetic functions, including photosynthesis and synthesis of fatty acids, essential amino acids and vitamins, are centered in chloroplasts, the work may have practical applications as people seek to modify, optimize, or otherwise control these capacities.