title: Formation of functional heterologous complexes using subunits from the picromycin, erythromycin and oleandomycin polyketide synthases.
abstract: BACKGROUND
  Recently developed tools for the genetic manipulation of modular polyketide synthases (PKSs) have advanced the development of combinatorial biosynthesis technologies for drug discovery. Although many of the current techniques involve engineering individual domains or modules of the PKS, few experiments have addressed the ability to combine entire protein subunits from different modular PKSs to create hybrid polyketide pathways. We investigated this possibility by in vivo assembly of heterologous PKS complexes using natural and altered subunits from related macrolide PKSs.
  
  
  RESULTS
  The pikAI and pikAII genes encoding subunits 1 and 2 (modules 1-4) of the picromycin PKS (PikPKS) and the eryAIII gene encoding subunit 3 (modules 5-6) of the 6-deoxyerythronolide B synthase (DEBS) were cloned in two compatible Streptomyces expression vectors. A strain of Streptomyces lividans co-transformed with the two vectors produced the hybrid macrolactone 3-hydroxynarbonolide. Co-expression of the same pik genes with the gene for subunit 3 of the oleandomycin PKS (OlePKS) was also successful. A series of hybrid polyketide pathways was then constructed by combining PikPKS subunits 1 and 2 with modified DEBS3 subunits containing engineered domains in modules 5 or 6. We also report the effect of junction location in a set of DEBS-PikPKS fusions.
  
  
  CONCLUSIONS
  We show that natural as well as engineered protein subunits from heterologous modular PKSs can be functionally assembled to create hybrid polyketide pathways. This work represents a new strategy that complements earlier domain engineering approaches for combinatorial biosynthesis in which complete modules or PKS protein subunits, in addition to individual enzymatic domains, are used as building blocks for PKS engineering.
authors.affiliation: Incorporated, KOSAN Biosciences, Hayward, CA 94545, USA. tang@kosan. com.
authors.forename: L
authors.initials: L
authors.lastname: Tang
authors.forename: H
authors.initials: H
authors.lastname: Fu
authors.forename: R
authors.initials: R
authors.lastname: McDaniel
mesh_terms: D000900:Anti-Bacterial Agents / Q000096:biosynthesis* / Q000737:chemistry; D004917:Erythromycin / Q000096:biosynthesis; D005798:Genes, Bacterial / Q000235:genetics; D005818:Genetic Engineering; D005822:Genetic Vectors / Q000138:chemical synthesis; D018942:Macrolides; D009097:Multienzyme Complexes / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics*; D005810:Multigene Family / Q000235:genetics; D009827:Oleandomycin / Q000096:biosynthesis; D020836:Protein Structure, Quaternary; D016930:Saccharopolyspora / Q000201:enzymology; D013302:Streptomyces / Q000201:enzymology; D013303:Streptomyces antibioticus / Q000201:enzymology
chemical_list: D000900:Anti-Bacterial Agents; D018942:Macrolides; D009097:Multienzyme Complexes; D004917:Erythromycin; C003145:picromycin; D009827:Oleandomycin