Biosynthetic Origin of the Rare Nitroaryl Moiety of the Polyketide Antibiotic Aureothin: Involvement of an Unprecedented N-Oxygenase

The antibiotic aureothin is a rare natural nitroaromatic compound produced by Streptomyces thioluteus. By labeling experiments, we demonstrate for the first time that p-nitrobenzoate (PNBA) serves as a polyketide synthase starter unit. Cloning, heterologous expression, and inactivation experiments reveal that this unusual primer is synthesized from p-aminobenzoate (PABA) by means of AurF, a novel N-oxygenase.