Required for the assembly and stabilization of PSII, but has no PPIases activity. [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Ubiquitous. Lower levels of expression in roots. Up-regulated by light. Down-regulated by dark. The N-terminal helical domain blocks the interaction with the potential target PSII subunit chlorophyll protein 47 (CP47). Stunted growth and hypersensitivity to high light.