# The Physiology of Oxidative Stress in Escherichia coli

> **NIH NIH R01** · UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN · 2023 · $11,867

## Abstract

We have learned that most oxidative toxicity arises when oxygen species attack enzymic iron
centers and that cellular defenses work by blocking, reversing, or by-passing the resultant
injuries. Yet key observations remain unexplained. In Aim 1 we will investigate why superoxide
stress precludes the use of sulfate as a sulfur source, and we will examine why thioredoxins and
glutaredoxins are strongly induced as part of the cellular reaction to hydrogen peroxide.
Extensive work has led us to the proposal that intracellular cysteine and redoxins help to repair
damaged metalloenzyme centers. This model would identify a key connection between sulfur
redox state and ROS.
Two enzymes dedicated to anaerobic metabolism—pyruvate:formate lyase activating enzyme
and alcohol dehydrogenase—have been suggested to be inactivated by iron-centered oxidation
events when cells are aerated. This would comprise a clever exploitation of reaction types that
are usually harmful. The goal of Aim 2 is to test this striking idea. This hypothesis leads to
notions of how the cell might seamlessly restore anaerobic metabolism when anoxia is restored.
Protein carbonylation (Aim 3) has long been used as a convenient marker of oxidative stress—
but the underlying events and physiological impact are unclear. Our data indicate that
carbonylation is focused upon relatively few proteins rather than the full proteome, and we
suspect that these proteins are mononuclear Fe(II) enzymes. Global mass spectrometry will
identify them by name. We will also test the idea that methionine sulfoxide is a disproportionate
Fenton product that reductases can repair. The novelty is that methionine may be oxidized by a
secondary electron-hopping event, rather than by direct attack.
Finally, in Aim 4 we will take a transcriptomic approach to fully define the OxyR peroxide
response. We hope to explain our discovery that OxyR activation per se compromises cells
fitness, to the point of prohibiting growth on acetate. It is not surprising that a stress response
should exert a price, but we do not yet recognize why any OxyR-driven adaptation would have
such a profound effect.
The emergent theme of oxidative stress is the tendency of oxygen species to react with iron
centers, and of cells to respond with layers of defensive tactics. Our four Aims will build upon
this knowledge by tackling persistent questions, with the overall goal of assembling a picture of
oxidative stress that is detailed, quantitative, and unified.

## Key facts

- **NIH application ID:** 10798735
- **Project number:** 3R01GM049640-29S1
- **Recipient organization:** UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN
- **Principal Investigator:** JAMES A. IMLAY
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2023
- **Award amount:** $11,867
- **Award type:** 3
- **Project period:** 1994-05-01 → 2025-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10798735

## Citation

> US National Institutes of Health, RePORTER application 10798735, The Physiology of Oxidative Stress in Escherichia coli (3R01GM049640-29S1). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10798735. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*