Fig. 1.

The rifamycin biosynthetic gene cluster and the role of AHBA synthase. a The rifamycin gene cluster from Amycolatopsis mediterranei. b The reaction catalyzed by AHBA synthase and the structure of rifamycin SV (the product of the rifamycin gene cluster). The rifamycin SV structure is colored according to the genes responsible for producing its PK core (red), AHBA-derived substructure (green), and tailoring functionalities (black). The phylogenetic divergence of AHBA synthase genes from previously characterized gene clusters correlates with the different structural classes of ansamycins