(469a) Analysis and Engineering of Modular Polyketide Synthase Systems

            Polyketide synthases (PKSs) are enzyme complexes that are incredible cellular machines involved in synthesis of molecules known as polyketides.  Polyketides are complex, organic molecules that have a variety of therapeutic applications, serving as antibacterial, anti-viral, and anti-cancer drugs.  A specific polyketide synthase, known as a modular PKS, assembles these compounds using an assembly line of modules (repeating protein subunits within the enzyme complex) that perform a step-by-step synthesis of the final product.  Since these enzymes are modular by nature, PKSs appear to be very attractive candidates for protein engineering.  Researchers have envisioned that by creating hybrid PKSs (assembly lines whose components come from PKSs originating in different organisms), novel polyketides could be synthesized, possessing new therapeutic properties.  Over the past two decades, attempts have been made to engineer new PKS complexes, but very few attempts have been met with success.  Furthermore, the body of knowledge relating to how full, intact PKS assembly lines function is very limited.

            With regards to improving engineering strategies for building hydrid PKSs, our lab has recently developed a model that explains the protein-protein interactions which are critical in the processing of polyketide intermediates.  Using this model as a guide, we have engineered new and improved non-natural PKS interfaces.  These studies have brought a deeper understanding of how these enzymes perform their catalysis and will hopefully pave the way for construction of novel PKS assembly lines.  In addition, we have recently demonstrated the full, in-vitro reconstitution of the 6-deoxyerythronolide B synthase (DEBS) which produces the macrocyclic precursor to the erythromycin family of antibiotics.  This reconstituted system has shed light on the kinetics and mechanism of full assembly-lines.  The convergence of both of these areas of research will hopefully make the engineering of novel PKS systems for biosynthesis of new polyketide therapeutics a reality.