# Analysis of a novel peptidoglycan assembly pathway in mycobacteria

> **NIH NIH R01** · UNIVERSITY OF ROCHESTER · 2020 · $601,557

## Abstract

Summary
 The burden of treating drug resistant TB and the emergence of new strains that are essentially resistant
to all TB drugs has prompted the re-assessment of ways to treat M. tuberculosis disease. One such treatment
modality is the use of the β-lactam class of antibiotics that target the peptide crosslinking pathways of bacterial
peptidoglycan (PG). These antibiotics are not used to treat M. tuberculosis infections due to the inherent
resistance of the bacteria via the BlaC β-lactamase. Nevertheless, M. tuberculosis can be killed by these
antibiotics in combination with the β-lactamase inhibitor clavulanic acid. This observation, made by us and
other groups, has renewed interest in exploiting β-lactam antibiotics as a way to treat TB infections. However,
knowledge of PG biosynthesis in mycobacteria has lagged behind that of other bacteria.
 Our overall research goals are to learn more about the assembly and maintenance of mycobacterial
peptidoglycan (PG). In this proposal, we are interested in the biological significance of novel 3-3 peptide
crosslinks within the PG. These linkages, first described in M. tuberculosis decades ago, are found in many
other bacteria but their significance in cell wall biology is poorly understood. The 3-3 crosslinks differ from
classical 4-3 crosslinks, also found in mycobacteria, in that 3-3 crosslinks are catalyzed by a novel pathway
that is distinct from the 4-3 crosslink pathway. While the 4-3 crosslinks are catalyzed by penicillin sensitive DD-
transpeptidases (also called penicillin-binding proteins or PBPs), the 3-3 crosslinks are made by unique,
penicillin insensitive LD-transpeptidases (Ldts). Our previous work has demonstrated that the mycobacterial
Ldt enzymes can be grouped into specific classes based upon sequence identity. Using M. smegmatis as a
surrogate organism we have constructed mutants with either single or multiple deletions of each of the ldt
genes and showed that only certain combinations of mutations yield mutant phenotypes. Central to all mutants
with a substantial phenotype is loss of the Class 5 ldtC gene, suggesting that LdtC is a key enzyme in this
pathway. This application aims to further examine the role of Ldt enzymes in M. tuberculosis cell wall biology,
with a particular focus on LdtC, and to characterize the role of DD-carboxypeptidases in the 3-3 crosslink
pathway.

## Key facts

- **NIH application ID:** 9963129
- **Project number:** 5R01AI139058-03
- **Recipient organization:** UNIVERSITY OF ROCHESTER
- **Principal Investigator:** Martin S. Pavelka
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $601,557
- **Award type:** 5
- **Project period:** 2018-07-01 → 2023-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9963129

## Citation

> US National Institutes of Health, RePORTER application 9963129, Analysis of a novel peptidoglycan assembly pathway in mycobacteria (5R01AI139058-03). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9963129. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*