# Cell-Wall Recycling and Nexus to Antibiotic Resistance

> **NIH NIH R35** · UNIVERSITY OF NOTRE DAME · 2022 · $386,250

## Abstract

Project Summary/Abstract
Cell-wall recycling is a fundamental process in bacteria, whereby it allows for remodeling of the cell wall in the
course of the normal growth and in response to antibiotics that inflict damage to the cell wall for their
mechanisms of action. Enterobacteriaceae and Pseudomonas aeruginosa (subject of this grant application)
sense damage inflicted to their cell wall by β-lactam antibiotics. The sensing event is linked to cell-wall
recycling, which leads to the formation of cell-wall-based natural products known as muropeptides. Certain
muropeptides are internalized to the cytoplasm, where they induce the bacterial response to the antibiotic
(antibiotic-resistance mechanisms). This process has led to obsolescence of many of the β-lactam antibiotics
against Gram-negative bacteria. My lab has studied this system for the past several years and what I disclose
in this MIRA application is the path that the lab will chart in the immediate future. I propose to study the
periplasmic complexes involving lytic transglycosylases (LTs), which turn over the cell wall for the purpose of
recycling or in response to damage by antibiotics. My lab has documented that there are 11 known LTs in P.
aeruginosa, whose individual reactions with the cell wall have been described by us. These enzymes are
proposed to be involved in complexes with other proteins within the periplasm, whose identities are not known
and represent a major gap in our knowledge of cell-wall processes. Whereas all the functions of LTs are not
understood, one is repair of cell wall upon exposure of bacteria to β-lactam antibiotics. Muropeptides are the
degradation products of cell-wall recycling, which are internalized to the cytoplasm for this purpose. As an
offshoot of the recycling events, certain muropetides activate the AmpR transcriptional regulator in expression
of the AmpC β-lactamase, the resistance determinant for β-lactam antibiotics. We will study the interactions of
the key mutropeptides with the AmpR protein in elucidating the system. Furthermore, four additional
cytoplasmic enzymes that have been identified in P. aeruginosa for the key events of the muropeptide
recycling will be investigated for their chemical reactions, the details of the catalytic cycles and for their
structures. I anticipate that the successful completion of this proposed science will not only lead to the
elucidation of these important events regulating the cell wall, but also will identify opportunities for their
interruption as a means to circumventing the elaborate mechanism of β-lactam resistance that Gram-negative
bacteria have evolved. These complex events are poorly understood, and they will be studied in detail in my
lab in the course of the proposed reseach.

## Key facts

- **NIH application ID:** 10401291
- **Project number:** 5R35GM131685-04
- **Recipient organization:** UNIVERSITY OF NOTRE DAME
- **Principal Investigator:** Shahriar Mobashery
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $386,250
- **Award type:** 5
- **Project period:** 2019-05-01 → 2024-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10401291

## Citation

> US National Institutes of Health, RePORTER application 10401291, Cell-Wall Recycling and Nexus to Antibiotic Resistance (5R35GM131685-04). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10401291. Licensed CC0.

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