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.