Constructing a model assembly line
A model of an assembly line composed of α-δ modules was constructed using the structures from the ESPript analysis. Domains were relatively positioned with PyMOL and polyalanine loops were built with Coot[18, 19]. The relative orientations of the domains were acquired from various crystal structures[20-22]; however, a 7-Å resolution electron microscopy reconstruction of a β-module with traditional boundaries from the pikromycin PKS shows a conformation of AT that is much closer to ACP and may be more accurate [8]. The coordinates of the model assembly line shown here can be freely downloaded from http://keatinge-clay.cm.utexas.edu/research/.