title: Knowledge-based design of bimodular and trimodular polyketide synthases based on domain and module swaps: a route to simple statin analogues.
abstract: BACKGROUND
  Polyketides are structurally diverse natural products that have a range of medically useful activities. Nonaromatic bacterial polyketides are synthesised on modular polyketide synthase (PKS) multienzymes, in which each cycle of chain extension requires a different 'module' of enzymatic activities. Attempts to design and construct modular PKSs that synthesise specified novel polyketides provide a particularly stringent test of our understanding of PKS structure and function.
  
  
  RESULTS
  We have constructed bimodular and trimodular PKSs based on DEBS1-TE, a derivative of the erythromycin PKS that contains only modules 1 and 2 and a thioesterase (TE), by substituting multiple domains with appropriate counterparts derived from the rapamycin PKS. Hybrid PKSs were obtained that synthesised the predicted target triketide lactones, which are simple analogues of cholesterol-lowering statins. In constructing intermodular fusions, whether between modules in the same or in different proteins, it was found advantageous to preserve intact the acyl carrier protein-ketosynthase (ACP-KS) didomain that spans the junction between successive modules.
  
  
  CONCLUSIONS
  Relatively simple considerations govern the construction of functional hybrid PKSs. Fusion sites should be chosen either in the surface-accessible linker regions between enzymatic domains, as previously revealed, or just inside the conserved margins of domains. The interaction of an ACP domain with the adjacent KS domain, whether on the same polyketide or not, is of particular importance, both through conservation of appropriate protein-protein interactions, and through optimising molecular recognition of the altered polyketide chain in the key transfer of the acyl chain from the ACP of one module to the KS of the downstream module.
authors.affiliation: Cambridge Centre for Molecular Recognition, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1GA, UK.
authors.forename: A
authors.initials: A
authors.lastname: Ranganathan
authors.forename: M
authors.initials: M
authors.lastname: Timoney
authors.forename: M
authors.initials: M
authors.lastname: Bycroft
authors.forename: J
authors.initials: J
authors.lastname: Cortés
authors.forename: I P
authors.initials: IP
authors.lastname: Thomas
authors.forename: B
authors.initials: B
authors.lastname: Wilkinson
authors.forename: L
authors.initials: L
authors.lastname: Kellenberger
authors.forename: U
authors.initials: U
authors.lastname: Hanefeld
authors.forename: I S
authors.initials: IS
authors.lastname: Galloway
authors.forename: J
authors.initials: J
authors.lastname: Staunton
authors.forename: P F
authors.initials: PF
authors.lastname: Leadlay
mesh_terms: D000595:Amino Acid Sequence; D015195:Drug Design; D000960:Hypolipidemic Agents / Q000737:chemistry; D007783:Lactones; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000235:genetics; D011487:Protein Conformation; D015202:Protein Engineering; D016930:Saccharopolyspora
chemical_list: D000960:Hypolipidemic Agents; D007783:Lactones; D009097:Multienzyme Complexes