The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, 76100, Israel.
Evogene Ltd., Rehovot, 76120, Israel.
Sci Rep. 2018 Mar 27;8(1):5230. doi: 10.1038/s41598-018-23578-x.
Degradation of the D1 protein of photosystem II (PSII) reaction center is a pre-requisite for the repair cycle from photoinhibition. Two types of thylakoid proteases, FtsH and Deg, have been demonstrated to participate in this process. However, the location of the proteolytic sites of the lumenal Deg1 protease within its internal sphere raised the question whether the lumenal-exposed regions of D1 are indeed long enough to reach these sites. Implanting these regions into the stable GFP rendered it sensitive to the presence of Deg1 in vitro, demonstrating that the flexible regions of D1 that protrude into the lumen can penetrate through the three side-openings of Deg1 and reach its internal proteolytic sites. This mode of action, facilitating cooperation between proteases on both sides of the thylakoid membranes, should be applicable to the degradation of other integral thylakoid membrane proteins as well.
光系统 II（PSII）反应中心 D1 蛋白的降解是光抑制修复循环的前提。两种类型的类囊体蛋白酶，FtsH 和 Deg，已被证明参与了这个过程。然而，腔内 Deg1 蛋白酶的蛋白水解位点位于其内部球体的位置提出了一个问题，即 D1 的腔暴露区域是否确实足够长以到达这些位点。将这些区域植入稳定的 GFP 中，使其对体外 Deg1 的存在敏感，证明了 D1 中伸向腔的灵活区域可以穿透 Deg1 的三个侧开口并到达其内部蛋白水解位点。这种作用模式促进了类囊体膜两侧蛋白酶之间的合作，也应该适用于其他整合的类囊体膜蛋白的降解。
