D1 is the main subunit of the complex which not only regulates the binding of cofactors, Antioxidants 2021, 10, 1216. https://doi.org/10.3390/antiox10081216 https://www.mdpi.com/journal/antioxidants Antioxidants 2021, 10, 1216 2 of 19 but also maintains the structure of the reaction center...