# Probing and Engineering of Iterative Polyketide Synthase

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA-IRVINE · 2021 · $279,831

## Abstract

PROJECT SUMMARY
 The objective of this proposal is to probe the regio-specificity of iterative type II
polyketide synthase (PKS) from bacteria, an enzyme complex comprised of 5 – 10 distinct
domains that produce pharmaceutically important natural products. Polyketide diversity is
achieved via a controlled variation of starter unit, chain length, and reduction/cyclization
patterns. The focus of this proposal is to use chemically synthesized polyketide mimics to
probe the regio-specificities of iterative PKS from bacteria (also called “type II PKS”).
Specifically, we wish to probe for chain length specificity of the ketosynthase (KS), stereo- and
regio-specificities of ketoreductase (KR), and cyclization specificity of aromatase/cyclase
(ARO/CYC). Understanding and controlling the regio-specificity of KS, KR and ARO/CYC can
potentially lead to new polyketide analogs with synthetic building blocks and new
ketoreduction/cyclization patterns. However, past attempt to solve cocrystal structures and to
understand the regio-specificity of PKS had been severely hampered by the chemical instability
of the poly-beta-ketone substrates. Oxetane has been developed as an isosteric mimic of
carbonyl groups. Here, for the first time, we propose to use oxetane as an isosteric substitute for
the carbonyl groups of poly-beta-ketone substrates for PKS. We will pursue the following
specific aims using a powerful combination of modern organic synthesis and structural biology:
AIM 1. Design and synthesis of oxetane-containing mimics of PKS intermediates (Vanderwal),
AIM 2. Determine Key Substrate-Protein Interactions in Priming and Elongating Ketosynthase
(Tsai), AIM 3. Determine Key Substrate-Protein Interactions in Ketoreductase (KR) and
Aromatase/Cyclase (ARO/CYC) Using the Oxetane Probes (Tsai), and AIM 4. Determine Key
Protein-Protein Interactions on the Timing of Chain Elongation, Ketoreduction and Cyclization
(Tsai). The outcomes will have high scientific impact, because it can potentially change
people’s vision about using chemical probes to approach PKS mechanism (Aim 1), elucidate
PKS regio-specificities (Aims 2-3), and provide the first type II PKS complex structure that
elucidates how protein-protein interactions affect product specificity (Aim 4). It therefore also
has potential high overall biomedical impact, because outcomes can be widely applied to
PKS bioengineering, leading to new polyketides with different chain length, reduction and
cyclization patterns that can subsequently be screened for new therapeutics and bioactivities.

## Key facts

- **NIH application ID:** 10113650
- **Project number:** 5R01GM127728-04
- **Recipient organization:** UNIVERSITY OF CALIFORNIA-IRVINE
- **Principal Investigator:** Shiou-Chuan Tsai
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $279,831
- **Award type:** 5
- **Project period:** 2018-06-10 → 2023-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10113650

## Citation

> US National Institutes of Health, RePORTER application 10113650, Probing and Engineering of Iterative Polyketide Synthase (5R01GM127728-04). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10113650. Licensed CC0.

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