Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340.
Copenhagen Plant Science Centre, Department of Plant and Environmental Sciences, University of Copenhagen, DK-1871 Frederiksberg C, Copenhagen, Denmark.
Proc Natl Acad Sci U S A. 2020 Jun 30;117(26):15354-15362. doi: 10.1073/pnas.2005832117. Epub 2020 Jun 15.
In photosynthetic electron transport, large multiprotein complexes are connected by small diffusible electron carriers, the mobility of which is challenged by macromolecular crowding. For thylakoid membranes of higher plants, a long-standing question has been which of the two mobile electron carriers, plastoquinone or plastocyanin, mediates electron transport from stacked grana thylakoids where photosystem II (PSII) is localized to distant unstacked regions of the thylakoids that harbor PSI. Here, we confirm that plastocyanin is the long-range electron carrier by employing mutants with different grana diameters. Furthermore, our results explain why higher plants have a narrow range of grana diameters since a larger diffusion distance for plastocyanin would jeopardize the efficiency of electron transport. In the light of recent findings that the lumen of thylakoids, which forms the diffusion space of plastocyanin, undergoes dynamic swelling/shrinkage, this study demonstrates that plastocyanin diffusion is a crucial regulatory element of plant photosynthetic electron transport.
在光合作用电子传递中，大型多蛋白复合物通过小分子可扩散电子载体连接，而这些载体的流动性受到大分子拥挤的挑战。对于高等植物的类囊体膜，一个长期存在的问题是，两种可移动的电子载体，质体醌或质体蓝素，哪一种介导电子从定位在 PSII 的堆叠类囊体到含有 PSI 的非堆叠类囊体的远距离区域的传递。在这里，我们通过使用具有不同堆叠直径的突变体来证实质体蓝素是长距离电子载体。此外，我们的结果解释了为什么高等植物具有较窄的堆叠直径范围，因为对于质体蓝素来说，更大的扩散距离将危及电子传递的效率。鉴于最近发现类囊体腔（形成质体蓝素扩散空间）经历动态膨胀/收缩的发现，本研究表明，质体蓝素扩散是植物光合作用电子传递的关键调节元件。
