Figure 7. Model of folding initiation in PpiA and its manipulation by the signal peptide.

Folding initiation in PpiA using foldons B (from the two N‐terminal β‐strands) and A as suggested by rigidification of early folding regions, H‐bonding and stabilized by native contacts (see text for details). The signal peptide causes disorder in the early mature domain and blocks this process either in “cis” (preventing stable H‐bonding in foldon B) or in “trans” (directly using parts of foldon B).