Fig. 7.

Mapping domain interactions in the DEBS PKS by mutant complementation analysis. The subunits used in this study were constructed by fusing the TE domain from module 6 to the C-terminus of the ACP domain in module 2. The site of a knockout mutation is indicated by X. The parental mutant homodimers were mixed together, the subunits were randomized to give a preparation consisting of hetero-and homodimers, then assayed for activity. Green arrows indicate which catalytic domains engage in functional interactions with an ACP domain and the directionality of intermodular substrate transfer. A red arrow indicates the blocked interaction responsible for an inactive heterodimer.