The D1 protein of Photosystem II (PSII) , encoded by the psbA genes, is a subunit of PSII reaction center and is an indispensable component of oxygenic photosynthesis. Due to strongly oxidative chemistry of PSII water splitting, the D1 protein is prone to constant photodamage requiring its replacement, whereas most of the other PSII subunits remain ordinarily undamaged.
