# A radical new paradigm for heme degradation in enteric pathogens

> **NIH NIH R01** · UNIVERSITY OF GEORGIA · 2020 · $306,832

## Abstract

PROJECT SUMMARY
For pathogens, the ability to acquire iron is critical and one of the best-understood indicators of virulence.
Numerous pathogenic organisms take advantage of the abundance of heme in the host cell and the human
diet as a source of essential iron. Until recently however, all of the known heme degrading enzymes required
molecular oxygen for function. In this project, we will investigate the mechanism of anaerobic heme
degradation in enterohemorrhagic E. coli (EHEC), a facultative anaerobic pathogen (e.g. O157:H7, which
causes bloody diarrhea, hemolytic uremic syndrome, kidney failure and death). We recently found that the
ChuW enzyme from EHEC catabolyzes heme and liberates iron under strictly anaerobic conditions. This
newly identified anaerobic heme degradation enzyme is part of an important module of heme utilization
proteins (ChuW, X, Y in E. coli) that is also found in other aggressive pathogens such as Vibrio cholerae.
Identification and characterization of this new pathway in enteric pathogens provides an unexplored
opportunity for developing novel antimicrobial compounds. In addition, the enzyme at the heart of this
investigation (ChuW) is a radical SAM methyltransferase (RSMT); it utilizes a [4Fe-4S] cluster to generate a
powerful radical species that facilitates the liberation of iron from heme through a methyl transfer reaction and
chemical rearrangement of the porphyrin. ChuW is capable of methylating an otherwise unreactive sp2-
hybridized carbon atom. Furthermore, ChuW is a member of the class C RSMTs, which are poorly understood
but have already been shown to catalyze key reactions in the biosynthesis of novel compounds with antitumor
and antibiotic properties. This work will provide new insight into this important class of RSMTs and how they
control highly reactive radicals to facilitate specific chemical conversions in the biosynthesis of compounds
including anti-microbial and anti-tumor agents. Using a multifaceted approach that combines traditional
enzyme kinetics, rigorous spectroscopic techniques, and modern structural biology tools, we will characterize
the mechanism of anaerobic heme degradation by ChuW, the properties of the anaerobic catabolites, and the
interplay of two additional proteins with ChuW in the anaerobic degradation of heme as well as the transport
and further reduction of the catabolites. The latter is important given recent work showing that heme
degradation products play a vital role in regulation of heme flux and iron homeostasis in other aggressive
pathogens. Our specific aims are to determine whether: ChuW catalyzes the liberation of iron from heme via a
radical SAM methyltransferase mechanism (using 5'-dAdo• and resulting in formation of “anaerobilin”) (Aim 1);
ChuX facilitates the chelation of the iron atom and delivery of “anaerobilin” to ChuY (Aim 3); and ChuY
catalyzes the NADPH-dependent reduction of anaerobilin to “anaerorubin” (Aim 2). Our long term goal is to
provide the necessar...

## Key facts

- **NIH application ID:** 9906908
- **Project number:** 5R01GM124203-04
- **Recipient organization:** UNIVERSITY OF GEORGIA
- **Principal Investigator:** WILLIAM N LANZILOTTA
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $306,832
- **Award type:** 5
- **Project period:** 2017-07-15 → 2023-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9906908

## Citation

> US National Institutes of Health, RePORTER application 9906908, A radical new paradigm for heme degradation in enteric pathogens (5R01GM124203-04). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/9906908. Licensed CC0.

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