Polyketide synthases (PKSs) of fungal origin are among the most enigmatic enzyme machineries known in microbial secondary metabolism. These enzymes are associated with the biosynthesis of very important fungal natural products, both beneficial, such as the cholesterol lowering blockbuster drug lovastatin from Aspergillus terreus; and deleterious, such as the carcinogenic mycotoxin aflatoxin from different aspergilli. The highly reducing fungal PKSs (HRPKS) are architecturally and mechanistically distinct from the well-characterized bacterial PKSs, and therefore produce compounds of different structural diversity and biological activities. In contrast to bacterial Type I PKSs or the structurally relatd mammalian FASs, our knowledge of the programming rules of fungal HRPKSs remains very limited, especially with regard to how a single set of domains are iteratively used and precisely orchestrated in the synthesis of the final product, often exceeding a combined 30 catalytic steps. Therefore, understanding fungal HRPKS function will enhance our knowledge of natural product biosynthesis and enzymology of multidomain, processive systems. In this proposal, we will comprehensively investigate the mechanisms of HRPKSs using several model systems and compounds. Our overarching goal is to understand, and to be able to predict, the relationship between HRPKS sequence and product structure.
Four aims will be pursued in parallel during the proposal period: 1) Classifying and mining fungal HRPKS based on function and product structure; 2) Fingerprinting the specificity of HRPKS tailoring domains; 3) Understanding protein-protein interactions in HRPKS off-loading mechanisms; and 4) Elucidating the enzymes responsible for post- PKS intramolecular cyclization reactions.
Each aim i s targeted at one unique aspect of HRPKS function that is vital to structural diversity generation. Fundamental enzymology questions will also be answered in addressing these aims. Our work tackles the least understood, the most difficult and perhaps the last frontier of polyketide biosynthesis.

Public Health Relevance

We propose to study the biosynthesis of the fungal polyketide synthases, which are large enzymes involved in the production of pharmaceutically important compounds. We are interested in understanding the mechanisms that govern the functions of these enzymes. Knowledge learned from this work can help us engineer these machineries towards producing different compounds for drug discovery purposes.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM085128-06
Application #
8817737
Study Section
Synthetic and Biological Chemistry B Study Section (SBCB)
Program Officer
Gerratana, Barbara
Project Start
2008-08-01
Project End
2018-11-30
Budget Start
2015-01-01
Budget End
2015-11-30
Support Year
6
Fiscal Year
2015
Total Cost
$337,573
Indirect Cost
$118,370
Name
University of California Los Angeles
Department
Engineering (All Types)
Type
Schools of Engineering
DUNS #
092530369
City
Los Angeles
State
CA
Country
United States
Zip Code
90095
Grandner, Jessica M; Cacho, Ralph A; Tang, Yi et al. (2016) Mechanism of the P450-Catalyzed Oxidative Cyclization in the Biosynthesis of Griseofulvin. ACS Catal 6:4506-4511
Gao, Shu-Shan; Duan, Abing; Xu, Wei et al. (2016) Phenalenone Polyketide Cyclization Catalyzed by Fungal Polyketide Synthase and Flavin-Dependent Monooxygenase. J Am Chem Soc 138:4249-59
Hang, Leibniz; Liu, Nicholas; Tang, Yi (2016) Coordinated and Iterative Enzyme Catalysis in Fungal Polyketide Biosynthesis. ACS Catal 6:5935-5945
Cochrane, Rachel V K; Sanichar, Randy; Lambkin, Gareth R et al. (2016) Production of New Cladosporin Analogues by Reconstitution of the Polyketide Synthases Responsible for the Biosynthesis of this Antimalarial Agent. Angew Chem Int Ed Engl 55:664-8
Sato, Michio; Winter, Jaclyn M; Kishimoto, Shinji et al. (2016) Combinatorial Generation of Chemical Diversity by Redox Enzymes in Chaetoviridin Biosynthesis. Org Lett 18:1446-9
Cacho, Ralph A; Tang, Yi (2016) Reconstitution of Fungal Nonribosomal Peptide Synthetases in Yeast and In Vitro. Methods Mol Biol 1401:103-19
Bond, Carly; Tang, Yi; Li, Li (2016) Saccharomyces cerevisiae as a tool for mining, studying and engineering fungal polyketide synthases. Fungal Genet Biol 89:52-61
Cochrane, Rachel V K; Gao, Zhizeng; Lambkin, Gareth R et al. (2015) Comparison of 10,11-Dehydrocurvularin Polyketide Synthases from Alternaria cinerariae and Aspergillus terreus Highlights Key Structural Motifs. Chembiochem 16:2479-83
Cacho, Ralph A; Thuss, Justin; Xu, Wei et al. (2015) Understanding Programming of Fungal Iterative Polyketide Synthases: The Biochemical Basis for Regioselectivity by the Methyltransferase Domain in the Lovastatin Megasynthase. J Am Chem Soc 137:15688-91
Mao, Xu-Ming; Zhan, Zha-Jun; Grayson, Matthew N et al. (2015) Efficient Biosynthesis of Fungal Polyketides Containing the Dioxabicyclo-octane Ring System. J Am Chem Soc 137:11904-7

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