Fig. 7. Illustration of possible intra- and inter-module conformations. (A and C) In the transfer conformation the PCP interacts with the A domain. The localization of the E domain is unknown. (B) In the epimerization conformation the PCP interacts with the E domain and the localization of the A domain is unknown. (D) In the donor condensation conformation the PCP is interacts with the donor position of the C domain. (E) In the acceptor condensation conformation the PCP interacts with the acceptor position of the C domain. The COM domains are essential to facilitate efficient intermodule interactions as shown in (D and E). Blue and yellow arrows indicate the proximities confirmed by photo-crosslinking, giving rise to L- and T-form crosslinks, respectively. (F) Graphical legend.