PPIases accelerate the folding of proteins. It catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides. Responsive of the major PPIase activity in the chloroplast thylakoid lumen. Regulates the accumulation of Rieske protein, an essential component of the photosynthetic electron transport chain. [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) PPIase activity is optimal in oxidized form (S-S) and minimal in reduced form (SH). Reduction of the oxidized form is mediated by thioredoxin (TRX-M). Interacts in vitro with LTO1 (PubMed:25412899). The precursor, but not the mature form of the protein, interacts with the Rieske protein. Expressed in stems, leaves and developing flower buds, but not in roots. The interaction between FKBP and the Rieske protein probably occurs before they are imported into the thylakoid. Belongs to the FKBP-type PPIase family.