title: Engineering a polyketide with a longer chain by insertion of an extra module into the erythromycin-producing polyketide synthase.
abstract: BACKGROUND
  Modular polyketide synthases catalyse the biosynthesis of medically useful natural products by stepwise chain assembly, with each module of enzyme activities catalysing a separate cycle of polyketide chain extension. Domain swapping between polyketide synthases leads to hybrid multienzymes that yield novel polyketides in a more or less predictable way. No experiments have so far been reported which attempt to enlarge a polyketide synthase by interpolating additional modules.
  
  
  RESULTS
  We describe here the construction of tetraketide synthases in which an entire extension module from the rapamycin-producing polyketide synthase is covalently spliced between the first two extension modules of the erythromycin-producing polyketide synthase (DEBS). The extended polyketide synthases thus formed are found to catalyse the synthesis of specific tetraketide products containing an appropriate extra ketide unit. Co-expression in Saccharopolyspora erythraea of the extended DEBS multienzyme with multienzymes DEBS 2 and DEBS 3 leads to the formation, as expected, of novel octaketide macrolactones. In each case the predicted products are accompanied by significant amounts of unextended products, corresponding to those of the unaltered DEBS PKS. We refer to this newly observed phenomenon as 'skipping'.
  
  
  CONCLUSIONS
  The strategy exemplified here shows far-reaching possibilities for combinatorial engineering of polyketide natural products, as well as revealing the ability of modular polyketide synthases to 'skip' extension modules. The results also provide additional insight into the three-dimensional arrangement of modules within these giant synthases.
authors.affiliation: Cambridge Centre for Molecular Recognition and Department of Biochemistry, University of Cambridge, UK.
authors.forename: C J
authors.initials: CJ
authors.lastname: Rowe
authors.forename: I U
authors.initials: IU
authors.lastname: Böhm
authors.forename: I P
authors.initials: IP
authors.lastname: Thomas
authors.forename: B
authors.initials: B
authors.lastname: Wilkinson
authors.forename: B A
authors.initials: BA
authors.lastname: Rudd
authors.forename: G
authors.initials: G
authors.lastname: Foster
authors.forename: A P
authors.initials: AP
authors.lastname: Blackaby
authors.forename: P J
authors.initials: PJ
authors.lastname: Sidebottom
authors.forename: Y
authors.initials: Y
authors.lastname: Roddis
authors.forename: A D
authors.initials: AD
authors.lastname: Buss
authors.forename: J
authors.initials: J
authors.lastname: Staunton
authors.forename: P F
authors.initials: PF
authors.lastname: Leadlay
mesh_terms: D003512:Cyclohexanones / Q000302:isolation & purification*; D004187:Disaccharides / Q000096:biosynthesis / Q000302:isolation & purification*; D004917:Erythromycin / Q000096:biosynthesis*; D009097:Multienzyme Complexes / Q000235:genetics* / Q000378:metabolism*; D016254:Mutagenesis, Insertional / Q000235:genetics*; D015202:Protein Engineering; D016930:Saccharopolyspora / Q000235:genetics / Q000378:metabolism
chemical_list: D003512:Cyclohexanones; D004187:Disaccharides; D009097:Multienzyme Complexes; C413265:tetraketide; D004917:Erythromycin