# The Physiology of Oxidative Stress in Escherichia coli

> **NIH NIH R01** · UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN · 2022 · $548,309

## 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:** 10458048
- **Project number:** 5R01GM049640-29
- **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:** 2022
- **Award amount:** $548,309
- **Award type:** 5
- **Project period:** 1994-05-01 → 2025-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10458048

## Citation

> US National Institutes of Health, RePORTER application 10458048, The Physiology of Oxidative Stress in Escherichia coli (5R01GM049640-29). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10458048. Licensed CC0.

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