Associated with the oxygen-evolving complex of photosystem II (PSII) (Probable). Is required for the stable binding of LHCSR3 to PSII-LHCII supercomplexes and is essential for efficient energy-dependent quenching and the integrity of the PSII-LHCII-LHCSR3 supercomplex under continuous high light (PubMed:25699588). Associated with the photosystem II complex. Belongs to the psbR family.