PPIases accelerate the folding of proteins. It catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides (By similarity). Involved in the accumulation of the PSII complex. [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Interacts in vitro with LTO1. PPIase activity is unaffected on reduction. Belongs to the FKBP-type PPIase family.