# Role of YxdJK and DAK in the Enterococcal Envelope Stress Response

> **NIH NIH K08** · METHODIST HOSPITAL RESEARCH INSTITUTE · 2022 · $185,759

## Abstract

Project Summary
This K08 Career Development Award application is intended to support the acquisition of skills and knowledge
needed to fulfill my long-term goal of becoming an independent physician-scientist focused on combating
antimicrobial resistant organisms, a serious threat to medical practice worldwide. Vancomycin resistant
enterococci (VRE) are an example of these pathogens and are a leading cause of healthcare associated
infections affecting critically ill and immunocompromised patients. VRE are categorized by the CDC as a
serious threat requiring the urgent development of novel therapeutic strategies. The lipopeptide antibiotic
daptomycin (DAP) is now a front line agent for VRE infections, but resistance to DAP can arise while on
therapy. The LiaFSR system, a major mediator of the cell envelope stress response, has been strongly
implicated in the development of DAP resistance. Inactivation of this system by deletion of the gene encoding
the LiaR response regulator was shown to re-sensitize enterococci to DAP. However, adaptation of LiaR
deficient strains of both clinical and laboratory origin resulted in DAP resistance, suggesting that alternate
pathways can protect the cell from antibiotic attack. Using whole genome sequencing of adapted strain pairs, I
identified two pathways with novel contributions to DAP and cephalosporin resistance in enterococci, i) the
YxdJK stress response system, and ii) the dihydroxyacetone kinase (DAK) domain protein involved in the
metabolism of extracellular fatty acids. The YxdJK system consists of a sensor histidine kinase (YxdK), a DNA
binding response regulator (YxdJ) and two ATP-binding cassette (ABC) transporters required to confer
resistance to bacitracin. Deletion of the gene encoding the YxdJ response regulator sensitizes Enterococcus
faecalis to both DAP and cephalosporins, despite a functional LiaFSR system. DAP-resistant strains using the
above pathways appear to display a very distinct mechanism of resistance to cell-envelope acting antibiotics.
This proposal is designed to dissect the role of the YxdJK system and the DAK enzyme in two major specific
aims. First, I will characterize the contributions of the YxdJK system to the cell envelope stress response to
antibiotics by defining how the system senses antibiotic stress and what genes are differentially expressed
when the system is active. Second, I will determine the DAK mediated changes that alter membrane
susceptibility to antibiotics, by comparing the membranes of wild type and DAK deletion strains to assess for
changes in phospholipids, envelope structure, membrane protein function, and biofilm formation. The Center
for Antimicrobial Resistance and Microbial Genomics (CARMiG) at the University of Texas Health Science
Center and adjacent institutions of the Texas Medical Center will provide an unparalleled environment to grow
as an investigator, with both an institutional commitment to combating antimicrobial resistance and an intensive
...

## Key facts

- **NIH application ID:** 10388366
- **Project number:** 5K08AI135093-06
- **Recipient organization:** METHODIST HOSPITAL RESEARCH INSTITUTE
- **Principal Investigator:** William R Miller
- **Activity code:** K08 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $185,759
- **Award type:** 5
- **Project period:** 2018-05-03 → 2023-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10388366

## Citation

> US National Institutes of Health, RePORTER application 10388366, Role of YxdJK and DAK in the Enterococcal Envelope Stress Response (5K08AI135093-06). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/10388366. Licensed CC0.

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