# Molecular mechanisms required for the maintenance of the gram-negative outer membrane

> **NIH NIH R01** · UNIVERSITY OF GEORGIA · 2022 · $409,560

## Abstract

Abstract
 The bacterial cell envelope is a remarkable and complex structure that guards bacteria from their
surrounding environment. A defining feature of gram-negative bacteria is the presence of an outer membrane
(OM) that encapsulates the peptidoglycan layer of these organisms. While the inner membrane (IM) is
composed of glycerophospholipids (GPLs), the OM is a bilayer with extreme lipid asymmetry with GPL
confined to the inner leaflet and lipopolysaccharide (LPS) localized to the outer leaflet. This unique membrane
organization affords gram-negative bacteria protection from large polar molecules, as well as lipophilic
compounds, serving as an essential innate barrier to a variety of antibiotics.
 However, once assembled, environmental factors can disrupt the LPS monolayer resulting in shedding of
LPS, and as a consequence, migration of GPLs from the inner leaflet to the outer leaflet of the OM. Extensive
formation of GPL rafts at the bacterial surface results in the loss of barrier function which leads to cell death.
To prevent this, the cell must maintain the OM asymmetry even under extreme environmental stress. The
overall objective of this application is to investigate the molecular mechanisms required for maintenance of
OM asymmetry, including the role of the recently identified Mla retrograde GPL transport system. We will also
investigate two additional systems, Pqi and Yeb systems, that may also serve in GPL transport. All three
systems (Mla, Pqi, and Yeb) are highly conserved across Gram-negative bacteria and disruption of OM
maintenance machinery has been shown to result in decreased virulence for many pathogens. The Specific
Aims of the current proposal are: (1) structure and functional analysis of Mla lipid binding proteins; (2) overall
architecture and protein-protein interactions of Mla components; and (3) investigation of lipid binding by GPL
transport systems in whole bacteria. Completion of the Aims will fill major gaps towards understanding
maintenance of OM asymmetry and provide new avenues for the generation of novel antimicrobials.

## Key facts

- **NIH application ID:** 10403653
- **Project number:** 5R01AI138576-05
- **Recipient organization:** UNIVERSITY OF GEORGIA
- **Principal Investigator:** Michael Stephen Trent
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $409,560
- **Award type:** 5
- **Project period:** 2018-06-01 → 2024-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10403653

## Citation

> US National Institutes of Health, RePORTER application 10403653, Molecular mechanisms required for the maintenance of the gram-negative outer membrane (5R01AI138576-05). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10403653. Licensed CC0.

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