# Molecular Mechanisms Regulating Bacterial Two-component Signaling Systems

> **NIH NIH R01** · UNIVERSITY OF IOWA · 2024 · $546,695

## Abstract

PROJECT SUMMARY/ABSTRACT
Staphylococcus aureus infections are a major global health problem and remain a significant health burden to
society. In the U.S. alone it is estimated that over three-hundred thousand cases of hospital-associated S.
aureus infections occur yearly at the cost of $2 billion. These infections also contribute to pneumonia, sepsis,
infective endocarditis, osteomyelitis, and other diseases. S. aureus infections and associated diseases result
from secreted virulence factors and the ability of the bacterium to survive in a wide range of environmental
niches, including hypoxic conditions. Importantly, growth and virulence are regulated by two-component
systems (TCS), which are composed of a membrane-bound sensor histidine kinase (HK) and a cytoplasmic
response regulator protein. The kinase senses the extracellular environment, and under the appropriate stimuli
transmits a signal across the cell membrane to induce phosphorylation of the response regulator, resulting in
changes in gene expression. The staphylococcus respiratory response AB (SrrAB) TCS is activated under
hypoxic conditions or in the presence of nitrosative stress and coordinates the regulation of virulence factors,
fermentation enzymes, nitric oxide detoxifying enzymes and biofilm formation. In this proposal, the PI will
pursue three aims designed to reveal the regulatory mechanisms of the SrrB sensor histidine kinase. The SrrB
HK is a transmembrane protein that contains an N-terminal extracellular Cache domain and a cytoplasmic
catalytic region (HAMP-PAS-DHpCA) containing a PAS domain. The first aim is to determine the role of the
SrrB PAS domain and how binding to heme impacts SrrB function. The second aim will identify ligands that
bind to the Cache domain and elucidate its sensing mechanism and role in virulence. The third aim will
determine the structural basis for SrrB enzymatic regulation using X-ray crystallography, SAXS and cryogenic
electron microscopy of full-length SrrB reconstituted in nanometer-scale lipid discs. Successful completion of
these studies will provide the molecular mechanism(s) by which SrrB senses extracellular ligands and cellular
redox to regulate catalytic function, and the biological consequences for disrupting this regulation. Our results
will have important implications for the design of novel therapeutic strategies targeting the SrrAB TCS to
combat antibiotic resistant S. aureus strains.

## Key facts

- **NIH application ID:** 10782545
- **Project number:** 5R01AI170557-02
- **Recipient organization:** UNIVERSITY OF IOWA
- **Principal Investigator:** Ernesto Jorge Fuentes
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $546,695
- **Award type:** 5
- **Project period:** 2023-02-08 → 2028-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10782545

## Citation

> US National Institutes of Health, RePORTER application 10782545, Molecular Mechanisms Regulating Bacterial Two-component Signaling Systems (5R01AI170557-02). Retrieved via AI Analytics 2026-06-12 from https://api.ai-analytics.org/grant/nih/10782545. Licensed CC0.

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