PPIase which accelerates the folding of proteins during protein synthesis. Has a preference for substrates containing 4-hydroxylproline modifications, including type III collagen. May also target type VI and type X collagens. [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Inhibited by tacrolimus/FK506. Monomer (PubMed:24821723, PubMed:24272907). Homodimer (PubMed:24821723, PubMed:24272907). Interacts with type III, type IV and type X collagens (PubMed:24821723). The disease is caused by variants affecting the gene represented in this entry.