Anovel degradation pathway of the D1 protein under light stress

在光胁迫条件下，光系统II结合D1蛋白的反应中心被快速降解。在本研究中，我们发现了一种新的D1降解途径。我们对该通路进行了详细的表征，并研究了该通路所涉及的成分。主要研究结果如下：1。从胞瘤中分离降解D1蛋白交联产物的蛋白酶：在光系统II的光抑制过程中，D1蛋白与周围多肽交联。我们使用明胶活性凝胶部分纯化了一种蛋白酶，该蛋白酶可以识别和消化基质部分的交联产物。利用光交联反应测定光系统II中D1蛋白及其邻近多肽的空间排列：我们测定了D1蛋白、CP43和doec33的相对排列。在光系统II的管腔侧。这些蛋白质对光系统II的出氧活性至关重要，并且在这里获得的信息对出氧系统的结构分析至关重要。热光胁迫下光系统II单线态氧的诱导以及D1蛋白与邻近多肽交联产物的生成：我们发现在热胁迫下光系统II光照下单线态氧的形成受到刺激。单线态氧是光系统II中蛋白质交联的主要原因。

Under light stress conditions, the reaction center binding D1 protein of photosystem II is degraded rapidly. In the present study, we found a novel pathway of D1 degradation. We characterized the pathway in detail and also studied the components involved in the pathway. The main results obtained are as follows :1. Isolation of a protease(s) degrading the cross-linked products of the D1 protein from the stioma : During the photoinhibition of photosystem II, the D1 protein cross-links with the surrounding polypeptides. We partiafly purified a protease(s) that recognizes and digests the cross-linked products from the fraction of stroma, using a gelatin activity gel.2. Determination of spatial arrangement of the D1 protein and neighboring polypeptides in photosystem II with the use of phofco-crossnnking reaction : We determined the relative arrangement of the D1 protein, CP43 andOEC33.in the lumenal side of photosystem II. These proteins are essential for the oxygen evolving activity of photosystem II, and the information obtained here is crucial for the structural analysis of the oxygen evolving system.3. Induction of singlet oxygen under heat and light stresses in photosystem II and the generation of cross-linked products of the D1 protein with the neighboring polypeptides : We found that formation of singlet oxygen by the illumination of PS II is stimulated under heat stress. The singlet oxygen was the main cause for the protein cross-linking in photosystem II.