Sequence, Cloning, and Analysis of the Fluvirucin B₁ Polyketide Synthase from <i>Actinomadura vulgaris</i>

Fluvirucin B₁, produced by <i>Actinomadura vulgaris</i>, is a 14-membered macrolactam active against a variety of infectious fungi as well as influenza A. Despite considerable interest from the synthetic community, very little information is available regarding the biosynthetic origins of the fluvirucins. Herein, we report the identification and initial characterization of the fluvirucin B₁ polyketide synthase and related enzymes. The cluster consists of five extender modules flanked by an N-terminal acyl carrier protein and C-terminal thioesterase domain. All but one of the synthase modules contain the full complement of tailoring domains (ketoreductase, dehydratase, and enoyl reductase) as determined by sequence homology with known polyketide synthases. Acitve site analyses of several key components of the cluster are performed to further verify that this gene cluster is associated with production of fluvirucin B₁. This work will both open doors toward a better understanding of macrolactam formation and provide an avenue to genetics-based diversification of fluvirucin structure