Rapid engineering of polyketide overproduction by gene transfer to industrially optimized strains |
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Authors: | Eduardo?Rodriguez Zhihao?Hu Sally?Ou Yanina?Volchegursky C?Richard?Hutchinson Email author" target="_blank">Robert?McDanielEmail author |
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Institution: | (1) Kosan Biosciences Inc, 3832 Bay Center Place, Hayward, CA 94545, USA |
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Abstract: | Development of natural products for therapeutic use is often hindered by limited availability of material from producing organisms.
The speed at which current technologies enable the cloning, sequencing, and manipulation of secondary metabolite genes for
production of novel compounds has made it impractical to optimize each new organism by conventional strain improvement procedures.
We have exploited the overproduction properties of two industrial organisms—Saccharopolyspora erythraea and Streptomyces fradiae, previously improved for erythromycin and tylosin production, respectively—to enhance titers of polyketides produced by genetically
modified polyketide synthases (PKSs). An efficient method for delivering large PKS expression vectors into S. erythraea was achieved by insertion of a chromosomal attachment site (attB) for φC31-based integrating vectors. For both strains, it was discovered that only the native PKS-associated promoter was
capable of sustaining high polyketide titers in that strain. Expression of PKS genes cloned from wild-type organisms in the
overproduction strains resulted in high polyketide titers whereas expression of the PKS gene from the S. erythraea overproducer in heterologous hosts resulted in only normal titers. This demonstrated that the overproduction characteristics
are primarily due to mutations in non-PKS genes and should therefore operate on other PKSs. Expression of genetically engineered
erythromycin PKS genes resulted in production of erythromycin analogs in greatly superior quantity than obtained from previously
used hosts. Further development of these hosts could bypass tedious mutagenesis and screening approaches to strain improvement
and expedite development of compounds from this valuable class of natural products. |
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Keywords: | Polyketide 6-Deoxyerythronolide B Erythromycin Tylosin Antibiotic |
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