Erythromycin A is produced by Saccharopolyspora erythraea via a secondary metabolic pathway using several steps including glycosylations and hydroxylations of the first macrolide intermediate 6-deoxyerythronolide B. Erythromycin C-12 hydroxylase (CYP113A1), the P450 cytochrome active in the final stages of erythromycin biosynthesis, was cloned and expressed in E. coli. Different crystal forms were harvested from distinct crystallization conditions: two ligand-free forms, one substrate bound and two inhibitors-bound. All crystals belong either to the monoclinc P21 or to the orthorhombic P212121 space groups, and exhibit diffraction limits ranging from 2.3 to 1.6 Å. The structures will be determined by molecular replacement. © 2008 Bentham Science Publishers Ltd.