The family of Deg proteases in Arabidopsis thaliana

Deg蛋白水解酶是存在于大多数生物体中的不依赖于ATP的丝氨酸内肽酶大家族的一部分。在人类和大肠杆菌中，这些蛋白水解酶与对各种胁迫的耐受性有关，而对它们在植物中的功能知之甚少。在A.thaliana数据库中进行同源搜索，发现了16个具有不同亚细胞位置的Deg同源物。根据进化关系，这些酶分为四个不同的组，其中组I在几乎所有生物中都有代表，组II(包含密切相关的Deg2和Deg9)在高等植物中是独一无二的。组III和组IV的差异最大，分别局限于高等植物和真菌(Deg7)或高等植物和哺乳动物(Deg15)。通过体外实验，我们证明了在光胁迫条件下，叶绿体Deg2蛋白酶降解光系统II反应中心的光损伤的D1蛋白，从而催化植物修复周期中的关键步骤。在这里，我们打算继续我们对叶绿体Deg2蛋白水解酶的研究：(A)解决体内底物识别和专一性的机制；(B)研究它在类囊体膜和基质中的双重定位；(C)分析复合体的形成和与其他组分的相互作用；(D)证明可能的伴侣活性及其在光系统II修复周期中的作用。此外，我们还希望将另外三种酶Deg7、Deg9、Deg15纳入我们的研究，并对这些酶进行详细的定位和表达研究，并寻找它们的生理靶点。

The Deg proteases are part of a large family of ATP-independent serine endopeptidases present in most organisms. In humans and Escherichia coli these proteolytic enzymes are implicated in the tolerance to various stresses, whereas very little is known about their functions in plants. homology searches in the A. thaliana database revealed the resence of 16 Deg homologues with a diverse subcellular location. Based on the evolutionary relationship these proteases cluster into four distinct groups, where group I has representatives in almost all organisms and group II (containing closely related Deg 2 and Deg9) is unique for higher plants. Group III and group IV are the most divergent and restricted to higher plants and fungi (Deg7) or higher plants and mammals (Deg15), respectively. Using in vitro assays we demonstrated that the chloroplast Deg2 protease degrades photodamaged D1 protein from the photosystem II reaction center under light stress conditions, thus catalyzing the key step in the repair cycle in plants. Here, we intend to continue our research on chloroplast Deg2 protease by: (a) solving a mechanism of the substrate recognition and specificity in vivo; (b) investigations of its dual location in the thylakoid membrane and stroma; (c) assaying the complex formation and interactions with other components and, (d) proving a possible chaperone activity and its role in photosystem II repair cycle. In addition, we would like to include three other proteases, Deg7, Deg9, Deg15, into our studies and to perform detailed localization and expression studies for these enzymes and to search for their physiological targets.