Page 1 |
Save page Remove page | Previous | 1 of 163 | Next |
|
small (250x250 max)
medium (500x500 max)
large ( > 500x500)
Full Resolution
All (PDF)
|
This page
All
Subset |
APPLICATION OF BIOLGICAL AND CHEMICAL APPROACHES TO GENERATE
NEW AND DIVERSE FUNGAL NATURAL PRODUCTS
by
Amber Dorothy Somoza
A Dissertation Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(CHEMISTRY)
August 2012
Copyright 2012 Amber Dorothy Somoza
Object Description
| Title | Application of biological and chemical approaches to generate new and diverse fungal natural products |
| Author | Somoza, Amber Dorothy |
| Author email | amber.somoza@gmail.com;amber.somoza@gmail.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Chemistry |
| School | College of Letters, Arts And Sciences |
| Date defended/completed | 2012-05-21 |
| Date submitted | 2012-08-02 |
| Date approved | 2012-08-02 |
| Restricted until | 2012-08-02 |
| Date published | 2012-08-02 |
| Advisor (committee chair) | Wang, Clay C. C. |
| Advisor (committee member) |
Roberts, Richard Olenyuk, Bogdan |
| Abstract | Filamentous fungi are prolific producers of bioactive secondary metabolites. Recent genome sequencing reveals fungi harbor more secondary metabolites than are currently known. Exploration of fungal secondary metabolism is more attractive today with recent advancements in genomics and molecular biology. Efficient gene-targeting technology is a powerful tool used to “mine” the genome for novel secondary metabolites and identify the genes in the biosynthetic pathway. Furthermore, this technology can be applied to engineering pathways to generate “unnatural” natural products. Integration of biosynthetic engineering with chemical synthesis can introduce greater structural diversity into natural products, a promising avenue for discovering therapeutic drugs. The current work describes strategies that utilize the strengths of biosynthetic engineering and chemical synthesis to generate novel fungal natural products. ❧ Genome mining efforts in Aspergillus nidulans revealed the novel azaphilone polyketide, asperfuranone; the first azaphilone with its biosynthetic pathway elucidated. Azaphilone natural products are structurally diverse and exhibit a variety of biological activities. We hypothesized the asperfuranone pathway can be reengineered to synthesize a putative intermediate to the azaphilone natural product, sclerotiorin, and apply chemical synthesis to access additional azaphilone compounds both natural and “unnatural”. Our strategy uses gene-targeting technology to replace the transcription factor, afoA, promoter with an inducible promoter and to knock out afoD, a gene that encodes for a hydroxylase, with the aim of leveraging the biosynthetic machinery to overproduce the putative intermediate, dimethyloctadiene benzaldehyde. Structural modifications utilizing synthetic chemistry transform the advanced intermediate into “unnatural” azaphilones in 2-3 steps. They were evaluated for biological activity against lipoxygenase-1 and provided a structure-activity relationship. ❧ To illustrate the potential of introducing diversity and generating novel compounds using a single biosynthetic pathway, a domain swapping strategy was applied to the pathway of asperfuranone. Our strategy to replace the loading domain of the native polyketide synthase (PKS), AfoE, with the loading domain of sterigmatocystin PKS would select for a different starter unit and alter the structure of asperfuranone. Identification of the linking regions between domains and utilization of gene-targeting technology allowed for the successfully assembly of the hybrid PKS. The engineered A. nidulans strain produced an unnatural naphthoquinone compound, revealing the hybrid PKS altered the polyketide backbone. Moreover, this work also suggested two domains within the non-reduced PKS are chiefly responsible for controlling chain length of the polyketide. Altogether, a single fungal biosynthetic pathway can be easily manipulated in multiple ways to produce potentially new bioactive metabolites highlighting the utility and value of combining chemical synthesis with biotechnology. |
| Keyword | Aspergillus; fungi; secondary metabolites; genetic engineering; biosynthesis |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m |
| Rights | Somoza, Amber Dorothy |
| Access conditions | The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright. The original signature page accompanying the original submission of the work to the USC Libraries is retained by the USC Libraries and a copy of it may be obtained by authorized requesters contacting the repository e-mail address given. |
| Repository name | University of Southern California Digital Library |
| Repository address | USC Digital Library, University of Southern California, University Park Campus MC 7002, 106 University Village, Los Angeles, California 90089-7002, USA |
| Repository email | cisadmin@usc.edu |
| Archival file | uscthesesreloadpub_Volume4/etd-SomozaAmbe-1125.pdf |
Description
| Title | Page 1 |
| Full text | APPLICATION OF BIOLGICAL AND CHEMICAL APPROACHES TO GENERATE NEW AND DIVERSE FUNGAL NATURAL PRODUCTS by Amber Dorothy Somoza A Dissertation Presented to the FACULTY OF THE USC GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (CHEMISTRY) August 2012 Copyright 2012 Amber Dorothy Somoza |
Comments
Post a Comment for Page 1
