Domains within the multienzyme polyketide synthases are linked by non-catalytic sequences of variable length and unknown function. Recently, the crystal structure was reported of a portion of the linker between the acyl-transferase (AT) and ketoreductase (KR) domains from module 1 of the erythromycin synthase (6-deoxyerythronolide B synthase), as a pseudo-dimer with the adjacent ketoreductase (KR).