The Study Of Function And Mechanism Of CTP Protease In Arabidopsis Thaliana

Chloroplast is an important organelle in green plant, which converts sunlight into the stable chemical energy by photosynthesis which almost guarantees the energy supply of the entire biosphere. Photosystem ? (PS?), a crucial part of the photosynthetic system, plays a decisive role in the photosynthetic electron transport chain process. In most photosynthetic organisms, D1 protein, the PS? core subunit, is synthesized as a precursor (pD1) and must be processed by CTP(C-terminal processing) protease to mature form (D1) to form PS? supercomplexes. PS? is a constantly assembly and repair complexes due to the easy damage characteristic of D1 protein embedded in the thylakoid membrane. The effective work of CTP protease guarantees photosynthesis normal function. In higer plant, there are three CTP proteins (CtpA,CtpB and CtpC), but the relationship of them remain unclear.In this paper, we conduct three aspects experiment to explore Arabidopsis thaliana CTP family protease. At first, I performed the CTP protease activity assay in vitro. The results show that the only CtpA can process pD1 protein C-terminal 9 animo acid extension and has high processing activity under high pH condition, and CtpB/CtpC were not capable of processing pD1 protein C-terminal 9 animo acid extension any detected pH condition; Second is about the other CTP protein expression test in a CTP family member null mutant. The result shows that the other CTP protein expression were not obvious distinction in CtpA or CtpC null mutant plant. Third is about transgenic plant assay, we transfer target gene with His tag gene sequence at its 3'-terminal into null mutant to next experiment, and aim at extracting proteins interacted with target protein by Affinity chromatography. According with acquired data, we conclude CTP family proteins have been divided into different function in the early stages of the evolution and to participate in the other life activities, but CtpA is the only one responsible for the D1 protein maturation.