PPIases accelerate the folding of proteins. It catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides. Has a regulatory effect on thylakoid protein phosphorylation. [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Does not bind cyclosporin A (CsA). Can interact with the inner surface of the stroma-exposed thylakoid regions.