PPIases accelerate the folding of proteins. It catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides. Binds double-stranded DNA in vitro. [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Inhibited by both FK506 and rapamycin. Phosphorylated by a nuclear kinase in the presence of Mg(2+) and ATP. Belongs to the FKBP-type PPIase family.