Biosynthesis of the bis-prenylated alkaloids muscoride A and B.

Prenylation is a common step in the biosynthesis of many natural products and plays an important role in increasing their structural diversity and enhancing biological activity. Muscoride A is a linear peptide alkaloid that contain two contiguous oxazoles and unusual prenyl groups that protect the amino and carboxy termini. Here we identified the 12.7 kb muscoride (mus) biosynthetic gene clusters from Nostoc spp. PCC 7906 and UHCC 0398. The mus biosynthetic gene clus-ters encode enzymes for the heterocyclization, oxidation, and prenylation of the MusE precursor protein. The mus gene clusters encodes two copies of the cyanobactin prenyltransfer-ase, MusF1 and MusF2. The predicted tetrapeptide substrate of MusF1 and MusF2 was synthesized through a novel tandem cyclization route in only eight steps. Biochemical assays demonstrated that MusF1 acts on the carboxy-terminus while MusF2 acts on the amino-terminus of the tetrapeptide sub-strate. We show that the MusF2 enzyme catalyzes the reverse or forward prenylation of amino-termini from Nostoc sp. PCC 7906 and UHCC 0398, respectively. This finding expands the regiospecific chemical functionality of cyanobactin prenyl-transferases and the chemical diversity of the cyanobactin family of natural products to include bis-prenylated polyoxa-zole linear peptides.