Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA.
Photosynth Res. 2022 Jun;152(3):283-288. doi: 10.1007/s11120-021-00886-4. Epub 2021 Nov 24.
The MnCa oxygen-evolving complex (OEC) in Photosystem II (PSII) is assembled in situ from free Mn, Ca, and water. In an early light-driven step, Mn in a protein high-affinity site is oxidized to Mn. Using dual-mode electron paramagnetic resonance spectroscopy, we observed that Mn accumulation increases as chloride concentration increases in spinach PSII membranes depleted of all extrinsic subunits. At physiologically relevant pH values, this effect requires the presence of calcium. When combined with pH studies, we conclude that the first Mn oxidation event in OEC assembly requires a deprotonation that is facilitated by chloride.
在光合作用系统 II（PSII）中，锰钙产氧复合物（OEC）是由游离的锰、钙和水原位组装而成的。在早期的光驱动步骤中，蛋白质高亲和力位点中的锰被氧化为 Mn。使用双模电子顺磁共振波谱法，我们观察到在菠菜 PSII 膜中，当所有外在亚基被耗尽时，氯离子浓度的增加会导致锰的积累增加。在生理相关的 pH 值下，这种效应需要钙的存在。当与 pH 值研究结合时，我们得出结论，OEC 组装中第一个锰氧化事件需要一个去质子化过程，氯离子促进了这个过程。
