Models for the interaction of PhsA, PhsB, and PhsC as well as TheA and TheB. (A) A fully functional TE motif is supposed to be present in PhsA. TheA and TheB have editing roles in PTT biosynthesis. (B) The TE motif in PhsA is not functional. One of the two TEs is involved in PTT release, and the other one has a corrective function. In both models, the order for the peptide synthetase assembly might be changed to PhsA, PhsC, and PhsB.