Understanding programming in highly reducing iterative fungal polyketide synthases - a structural and mechanistic approach

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Fungal polyketide synthases (PKS) are extremely large multifunctional multi-domain proteins that assemble simple biochemical building blocks in a highly programmed iterative manner to make a huge range of biologically active complex natural products many of which are of importance as drugs or agrochemical agents or as toxins which are detrimental to both human health and agriculture. In simple terms PKSs are like beads on a string where each bead or 'domain' of the PKS represents an individual enzyme function or biological catalyst. The PKS uses simple carbon-carbon bond forming (condensation) reactions followed by a variety of 'tailoring' reactions in which the initial condensation product may be modified by all or some of a series of reactions - reduction (addition of two atoms of hydrogen), dehydration (loss of water) and C-methylation (addition of a single carbon branch), each of which is controlled by specific domains on the PKS. Discovering the molecular factors which control this programming is arguably the greatest remaining problem in our understanding of how nature makes complex natural products, and also represents a great fundamental problem in enzyme catalysis. Understanding of how the programming works, how the number iterative condensation cycle that determines the overall chain length, degree of reduction, and methylation is essentially absent. In this project the individual beads/domains will be isolated so that their individual properties and structures can be studied. Individual beads will then be brought together to study how one influences another, and this process will be repeated to try to build up an overall picture of how the intact PKS works. The project is highly interdisciplinary and will bring together the skills and expertise of natural products chemistry, chemical synthesis, molecular biology, biochemistry, structural biology and bioinformatics. The ultimate aim is to use the understanding gained of how the programming actually works, to manipulate the PKSs to make new products with altered or improved properties of benefit to human and animal health and to provide the pharmaceutical and fine chemical industries with new methods to produce new useful products.