# Conformational Properties of Cytochromes in Disease

> **NIH NIH R01** · DARTMOUTH COLLEGE · 2020 · $303,788

## Abstract

Bacteria frequently encounter microoxic environments, particularly in dense communities associated with
biofilms, sites of infection, and in symbiotic life. Microbes have evolved to respire O2 even when its
concentrations are low but the mechanisms that underlie microoxic respiration are not well understood. In
many bacteria, including Pseudomonas aeruginosa (Pa), O2 reduction to water is catalyzed by cbb3 terminal
oxidases that have several features distinct from those of mammalian oxidases. Success of four-electron O2
reduction depends on the coordinated play of multiple redox centers and, under microoxic conditions, also on
regulatory mechanisms to deal with the limited supply of O2. We have identified two metalloproteins critical for
the microoxic function of cbb3 oxidases in Pa: the electron carrier cytochrome c4 (cyt c4) and the O2 carrier
hemerythrin (Hr); both of them are required for robust Pa growth at low O2. Cbb3 oxidases in Pa and many
other proteobacteria have an extended chain of six metal redox centers and their electron carrier has two. We
propose that diheme architecture of cyt c4 and the extended electron-transfer (ET) chain in cbb3 oxidases,
together with unique conformational dynamics, are used to modulate ET through these respiratory proteins
providing opportunities for regulation of the redox flow and enabling efficient energy conversion during
catalysis. Furthermore, we hypothesize that Hr aids in directing O2 for use in respiration by membrane-bound
Pa cbb3 oxidases. In this project, the spectroscopic and electrochemistry studies of protein components and
their interactions in vitro are combined with genetics and phenotypic analyses in vivo to (1) characterize the
role of diheme moieties in regulating ET properties of cyt c4 and of the CcoP subunit of cbb3 oxidase and
establish the mechanism of the electron injection to the enzyme; (2) elucidate the mechanism of electron flow
within the extended ET chain in cbb3 oxidase and coordination of conformational changes with ET steps; and
(3) establish the mechanism of effects of Hr on the function of cbb3 oxidase in Pa. The proposed studies of
cbb3 oxidases will provide a foundation for understanding the molecular mechanisms that enable bacteria to
thrive in low-O2 environments and identifying strategies that may disrupt bacterial growth in these settings.
With our focus on redox cooperativity, conformational gating, proton-coupled processes, and regulatory protein
networks, our studies will address important topics in biological redox mechanisms relevant to function of many
other metalloproteins that play a role in human health.

## Key facts

- **NIH application ID:** 9886350
- **Project number:** 2R01GM098502-06A1
- **Recipient organization:** DARTMOUTH COLLEGE
- **Principal Investigator:** Ekaterina PLETNEVA
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $303,788
- **Award type:** 2
- **Project period:** 2011-08-01 → 2023-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9886350

## Citation

> US National Institutes of Health, RePORTER application 9886350, Conformational Properties of Cytochromes in Disease (2R01GM098502-06A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9886350. Licensed CC0.

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