Figure 1.

Schematic diagram of the modular organization of 6-deoxyerythronolide B synthase (DEBS). Three polypeptides (DEBS1, DEBS2, and DEBS3) each contain two modules that are, in turn, composed of distinct catalytic domains. KS indicates ketosynthase; AT, acyl transferase; KR, ketoreductase; ACP, acyl carrier protein; DH, dehydratase; ER, enoyl reductase; and TE, thioesterase. DEBS1 also contains a loading didomain, consisting of an AT and an ACP. KR⁰ denotes an inactive KR domain. Inter-protein linker (docking) domains are shown as matching tabs.