# Iterative Polyketide Synthase Function, Structure and Pathways

> **NIH NIH R01** · JOHNS HOPKINS UNIVERSITY · 2022 · $458,333

## Abstract

The importance of polyketides to human health and welfare is recognized both by major pharmaceuticals
and important environmental carcinogens and mammalian toxins, as well as phytotoxins that impose heavy
costs on agriculture and endanger the food supply. In three major Aims, we propose to undertake fundamental
biochemical and structural studies of representatives from two major families of iterative polyketide synthases,
which exemplify some of the most sophisticated catalytic systems known and pose many unanswered questions
about how the coordinated function of their individual catalytic domains is achieved. Unequivocal
determination of the programmed product of the enediyne highly-reducing (HR)-PKSs will be extended to
investigation of how this simple, shared intermediate is converted to the enediyne and anthraquinone “halves”
of dynemicin A and other enediyne architectures.
 With advances in antibody technology, conjugates of enediyne natural products are coming again as
valuable anti-cancer therapies. The biosynthesis of these structurally intriguing DNA-cleaving molecules
remains one of the principal unsolved problems in natural product biosynthesis. Application of precise
CRISPR/Cas9 gene deletions in the dynemicin A pathway has brought exciting experimental advances to isolate
and characterize the first post-PKS intermediates in any enediyne biosynthetic pathway. Additional mutational
studies will be carried out, the structures of other possible intermediates will be elucidated and a strategy of
paired CRISPR mutations will be developed to finally crack how these fascinating structures are made.
 Having first detected and functionally characterized “starter-unit acyl transferase” (SAT) domains and
“product template” (PT) domains in NR-PKSs, we are now poised to build from static structures of individual
domains, stepwise to tridomains and tetradomains to, finally, full-length structures. In this Aim collaboration
with the laboratory of Timm Maier (Biozentrum, Univ. of Basel) will couple biochemical studies, ACP–client
crosslinking, x-ray crystallography and cryo-electron microscopy to achieve the next level of understanding to
visualize how these separate components integrate their actions into fully functional molecular machines.
 Cercospora sp. cause immense damage to a range of vital food crops through the production of
cercosporin, a diabolically efficient photosensitizer of reactive oxygen species and pathogenic to plants (and
animals). The mostly unexplored biosynthesis of this perylenequinone will be undertaken and previous
biogenetic proposals will be corrected. The roles of a laccase/fasciclin-family protein and other newly discovered
biosynthetic proteins encoded in an expanded biosynthetic gene cluster will be studied in collaboration with
scientists at the USDA with the added goal to find “green” ways to combat toxin production by this pathogen.
!

## Key facts

- **NIH application ID:** 10319955
- **Project number:** 5R01ES001670-43
- **Recipient organization:** JOHNS HOPKINS UNIVERSITY
- **Principal Investigator:** CRAIG ARTHUR TOWNSEND
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $458,333
- **Award type:** 5
- **Project period:** 1978-02-01 → 2023-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10319955

## Citation

> US National Institutes of Health, RePORTER application 10319955, Iterative Polyketide Synthase Function, Structure and Pathways (5R01ES001670-43). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10319955. Licensed CC0.

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