# Studies on the Biological Mechanisms of Antibiotics

> **NIH NIH R01** · HARVARD UNIVERSITY · 2020 · $628,109

## Abstract

Project Summary/Abstract
Antibiotic-resistant Gram-negative infections pose a serious threat to human health. The outer membrane of
Gram-negative bacteria is a unique structure essential for survival; it also functions as a physical barrier to block
entry of many classes of antibiotics, thereby rendering them ineffective. At present, colistin is the only antibiotic
active against many resistant Gram-negative infections, but it has dose-limiting toxicity. We have discovered that
the DNA gyrase inhibitor novobiocin and analogs with no gyrase activity potentiate the activity of colistin. Based
on genetic, structural, and biochemical data, we propose that they do so by binding to and activating the inner
membrane lipopolysaccharide transport complex. The inner membrane complex uses the energy of ATP
hydrolysis by a cytoplasmic ATPase (LptB) to extract lipopolysaccharide from the inner membrane and move it
onto a protein bridge that spans the periplasm to the outer membrane. We have shown that novobiocin binds at
the interface between LptB and LptFG, the transmembrane components of the transporter. We have also shown
that another component of the transporter, LptC, couples the energy of ATP hydrolysis to LPS extraction from
the membrane. We propose experiments to better understand how LptC coordinates ATP hydrolysis with LPS
extraction because this information is integral to understanding how novobiocin activates the machine. We also
propose to develop new assays to quantify binding of novobiocin analogs and to monitor machine dynamics. We
will apply these assays to characterize new synthetic analogs of novobiocin. Our objective is to identify
compounds that strongly activate the transport machine while retaining gyrase activity. We will test compounds
for synergy with colistin to test the hypothesis that strong activation of the transport machine is required for good
synergy. This work may lead to development of safer colistin-based therapies to treat Gram-negative infections.
In addition, the fundamental knowledge obtained about how this transporter works could enable discovery of
other classes of compounds that interfere with its function.

## Key facts

- **NIH application ID:** 9885644
- **Project number:** 9R01AI149778-17
- **Recipient organization:** HARVARD UNIVERSITY
- **Principal Investigator:** Daniel Kahne
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $628,109
- **Award type:** 9
- **Project period:** 2002-07-01 → 2024-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9885644

## Citation

> US National Institutes of Health, RePORTER application 9885644, Studies on the Biological Mechanisms of Antibiotics (9R01AI149778-17). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/9885644. Licensed CC0.

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