# MOLECULAR STUDY OF PHA BIOSYNTHESIS: PRODUCTION OF BIODEGRADABLE POLYMERS FOR MEDICAL APPLICATIONS

> **NIH NIH R01** · KANSAS STATE UNIVERSITY · 2020 · $90,000

## Abstract

Polyhydroxyalkanoates (PHAs) are polyoxoesters produced by a wide range of bacteria under nutrient-limited
growth conditions except for carbon. Due to their excellent biocompatibility, biodegradability, and versatility,
PHAs have been developed for various biomedical applications in medical devices, drug delivery, and tissue
engineering. The FDA approved the first medical use of PHAs in 2009 as an absorbable suture under the trade
name TephaFLEX. However, the high cost of PHA production has been an impediment to their further
development and downstream commercialization. Our goal is to identify and understand the complete PHA
biosynthetic machinery so that PHAs with defined properties can be produced economically. To facilitate this,
the present proposal will focus on the PHA synthase (PhaC) and phasin protein (PhaP), which are key to both
PHA production and the properties of the material produced. The specific aims are: (1) to characterize the
mechanism of PhaC in PHA production and control of molecular weight (MW). We will investigate chain
elongation of class I synthases that are much more challenging than the class III enzymes using multiple
approaches involving enzymology, molecular biology, and synthetic chemistry. Efforts will also be made to look
for the “additional factors” that are proposed to participate in the control of PHA MWs using genetically
modified organisms. Protein-protein interactions will be identified through pull-down assays for strong
interactions and by incorporating photoactive unnatural amino acids for weak interactions. The MW control by
PhaC itself will also be studied in vitro through a synthetic analog or in vivo through identifying the residues
involved in the chain termination/re-initiation processes; (2) to obtain structural information on PHA synthases
through X-ray crystallography. In collaboration with Dr. Geisbrecht who is an accomplished crystallographer on
the same campus, synthases from different bacterial sources will be purified and screened for crystallization in
the absence and presence of ligands. Our preliminary results of co-crystallization with a nonhydrolyzable CoA
analog have provided a clear path toward an initial PhaC structure. The availability of this X-ray structure will
provide us with valuable insight on substrate recognition and enzyme mechanism as well as enabling our long-
term goal of protein engineering; (3) to characterize roles of PhaP in PHA production and granule formation.
The relationship of PhaC and PhaP will be characterized in vitro and in vivo using various binding assays and
with Escherichia coli supplemented with a PHA biosynthetic pathway. Granule formation will be monitored in
vivo for the first time through a combination of fluorescence microscopy and click-chemistry. Elucidating the
roles and relationships of PhaC, PhaP, “additional factors” and granule (PHA) formation at the molecular level
is of great importance to complete our understanding of PHA production. Ulti...

## Key facts

- **NIH application ID:** 10135429
- **Project number:** 3R01GM117259-05S1
- **Recipient organization:** KANSAS STATE UNIVERSITY
- **Principal Investigator:** Ping Li
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $90,000
- **Award type:** 3
- **Project period:** 2016-05-05 → 2023-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10135429

## Citation

> US National Institutes of Health, RePORTER application 10135429, MOLECULAR STUDY OF PHA BIOSYNTHESIS: PRODUCTION OF BIODEGRADABLE POLYMERS FOR MEDICAL APPLICATIONS (3R01GM117259-05S1). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10135429. Licensed CC0.

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