| Description |
Natural products are structurally complex molecules and often exhibit intriguing biological activities. They are, however, notoriously difficult to supply, whether by chemical synthesis or isolation from a living organism. Recently, reconstitution of natural product biosynthetic pathways in a heterologous host has proved a successful strategy for producing natural products in vivo, but has rarely achieved the level of sustainability desired for medicinal applications. This approach is limited by our lack of understanding of biosynthesis and pathway expression. The focus of this dissertation is biosynthetic strategies for the supply of therapeutically-relevant natural products. Two examples are included, one involving a biosynthetic outlook of a known family of compounds with an uncharacterized metabolic origin, and a second uniting discovery, production, and biological characterization of a novel anti-HIV compound. The adociasulfates are a family of marine sponge-derived meroterpenes known to inhibit kinesin, making them attractive anticancer drug leads. Despite difficulties in synthesizing adociasulfates, biosynthesis has never been investigated as a potential means of production. In Chapter 1, detailed consideration is given to the biosynthetic origin of these compounds, revealing a set of just four possible precursors for all sponge merotriterpenes. The mechanism of action of adociasulfates, addressed in Chapter 2, was shown to occur in a 1:1 interaction with kinesin, contrary to previous reports of microtubule-mimicking aggregates. Adociasulfates are thus shown to be valuable tools for the study of kinesin and maintain potential therapeutic importance, making their production an ever more important goal. The discovery, production, and biological characterization of an anti-HIV lanthipeptide, divamide A, is described in Chapter 3. The divamides were discovered from small tunicates from Papua New Guinea. By integrating structure- and genomics-based methodologies, we were able to elucidate the structure of a small amount of isolated material. This approach also provided us with a biosynthetic platform from which heterologous expression and sustainable production were achieved in Escherichia coli. The structure activity relationships of the divamides show that functional diversity is achieved by introducing minor structural changes to a conserved chemical scaffold Finally, an extended family of related peptides was identified that bears some of the hallmarks of known diversity-generating pathways. |
