Essential protein that plays a major role in protein secretion by helping the post-translocational extracellular folding of several secreted proteins. Has PPIase activity but it is not essential for its function in vivo. [protein]-peptidylproline (omega=180) = [protein]-peptidylproline (omega=0) Present in detergent-resistant membrane (DRM) fractions that may be equivalent to eukaryotic membrane rafts; these rafts include proteins involved in signaling, molecule trafficking and protein secretion. All three domains (PPIase domain and the flanking N- and C-terminal domains) are essential for activity. Belongs to the PrsA family. Sequencing errors. The N-terminus of this sequence is probably the N-terminus of phrI.