Bill Broadhurst

Bill Broadhurst

Structural dynamics of modular polyketide synthases.

Modular polyketide synthases (PKSs) are among the largest integrated enzyme complexes known, organizing clusters of catalytic domains into assembly lines which produce bioactive products that range from antibiotics to toxins. We are interested in how these systems use global conformational changes and the recognition of transient interfaces to control the growth of polyketide chains.

The key players in each module are acyl carrier protein (ACP) domains, which serve as attachment points for the growing substrate chain and shuttle intermediates between each active site. Focusing on the system that produces the toxin mycolactone, we have used NMR spectroscopy and isothermal calorimetry to demonstrate that processes in PKS systems can occur using fundamentally different mechanisms. For example, specific protein-protein and protein-prosthetic group interfaces are required for ACP and ketoreductase domains to interact, but release of the final polyketide product from ACP by a terminal thioesterase domain is governed solely by recognition of the correct substrate chemistry.

Our findings have important implications for attempts to engineer modified PKS systems that make novel compounds.

Research objectives

  • How does the quaternary structure of a PKS module rearrange during a catalytic cycle?

  • Does ACP domain structure influence the programming of complex PKS mega-enzymes?

  • Can mutagenesis 'precision surgery' expand the substrate selectivity and reaction specificity of PKS systems?

  • Are there rules that could guide the assembly of hybrid PKS systems to make novel molecules?

  • Can bioinformatics tools predict the structures of new natural products by analysing environmental DNA?

Key publications

Moretto L, Heylen R, Holroyd N, Vance S, Broadhurst RW (2019). Modular type I polyketide synthase acyl carrier protein domains share a common N-terminally extended fold. Sci. Rep., 9(1):2325. doi: 10.1038/s41598-019-38747-9

Moretto L, Vance S, Heames B, Broadhurst RW (2017). Dissecting how modular polyketide synthase ketoreductases interact with acyl carrier protein-attached substrates. Chem. Commun., 53(83):11457-11460. doi: 10.1039/c7cc04625a

Vance S, Tkachenko O, Thomas B, Bassuni M, Hong H, Nietlispach D, Broadhurst W (2016). Sticky swinging arm dynamics: studies of an acyl carrier protein domain from the mycolactone polyketide synthase. Biochem. J., 473(8):1097-1110. doi: 10.1042/BCJ20160041

Murphy AC, Hong H, Vance S, Broadhurst RW, Leadlay PF (2016). Broadening substrate specificity of a chain-extending ketosynthase through a single active-site mutation. Chem. Commun., 52(54):8373-8376. doi: 10.1039/c6cc03501a

Broadhurst RW, Nietlispach D, Wheatcroft MP, Leadlay PF, Weissman KJ (2003). The structure of docking domains in modular polyketide synthases. Chem. Biol., 10(8):723-731. doi: 10.1016/s1074-5521(03)00156-x