Identification of the chelocardin biosynthetic gene cluster from Amycolatopsis sulphurea: a platform for producing novel tetracycline antibiotics

• DOI: 10.1099/mic.0.070995-0
• Publication Date: 2013-09-17T02:21:07Z
• Authors: Tadeja Lukežič; Urška Lešnik; Ajda Podgoršek; Jaka Horvat; Tomaž Polak; Martin Šala; Branko Jenko; Peter Raspor; Paul R. Herron; Iain S. Hunter; Hrvoje Petković
• Keywords: DNA, Bacterial; 0301 basic medicine; 570; 0303 health sciences; Molecular Sequence Data; Sequence Analysis, DNA; Anti-Bacterial Agents; Biosynthetic Pathways; 3. Good health; Open Reading Frames; 03 medical and health sciences; Pharmacy and materia medica; Tetracyclines; Multigene Family; 616; Actinomycetales

Tetracyclines (TCs) are medically important antibiotics from the polyketide family of natural products. Chelocardin (CHD), produced by Amycolatopsis sulphurea, is a broad-spectrum tetracyclic antibiotic with potent bacteriolytic activity against a number of Gram-positive and Gram-negative multi-resistant pathogens. CHD has an unknown mode of action that is different from TCs. It has some structural features that define it as 'atypical' and, notably, is active against tetracycline-resistant pathogens. Identification and characterization of the chelocardin biosynthetic gene cluster from A. sulphurea revealed 18 putative open reading frames including a type II polyketide synthase. Compared to typical TCs, the chd cluster contains a number of features that relate to its classification as 'atypical': an additional gene for a putative two-component cyclase/aromatase that may be responsible for the different aromatization pattern, a gene for a putative aminotransferase for C-4 with the opposite stereochemistry to TCs and a gene for a putative C-9 methylase that is a unique feature of this biosynthetic cluster within the TCs. Collectively, these enzymes deliver a molecule with different aromatization of ring C that results in an unusual planar structure of the TC backbone. This is a likely contributor to its different mode of action. In addition CHD biosynthesis is primed with acetate, unlike the TCs, which are primed with malonamate, and offers a biosynthetic engineering platform that represents a unique opportunity for efficient generation of novel tetracyclic backbones using combinatorial biosynthesis.