Maturing Mycobacterium smegmatis peptidoglycan requires non-canonical crosslinks to maintain shape
- Harvard TH Chan School of Public Health, United States
- Harvard Medical School, United States
- Swiss Federal Institute of Technology in Lausanne (EPFL), Switzerland
- Texas A&M University, United States
- Yale School of Medicine, United States
Abstract
In most well studied rod-shaped bacteria, peptidoglycan is primarily crosslinked by penicillin-binding proteins (PBPs). However, in mycobacteria, crosslinks formed by L,D-transpeptidases (LDTs) are highly abundant. To elucidate the role of these unusual crosslinks, we characterized Mycobacterium smegmatis cells lacking all LDTs. We find that crosslinks generate by LDTs are required for rod shape maintenance specifically at sites of aging cell wall, a byproduct of polar elongation. Asymmetric polar growth leads to a non-uniform distribution of these two types of crosslinks in a single cell. Consequently, in the absence of LDT-mediated crosslinks, PBP-catalyzed crosslinks become more important. Because of this, Mycobacterium tuberculosis (Mtb) is more rapidly killed using a combination of drugs capable of PBP- and LDT- inhibition. Thus, knowledge about the spatial and genetic relationship between drug targets can be exploited to more effectively treat this pathogen.
Data availability
Sequencing data were deposited into NCBI's Sequence Read Archive (SRA) under SRA study- SRP141343 https://www.ncbi.nlm.nih.gov/Traces/study/?acc=SRP141343
Article and author information
Author details
Catherine Baranowski
Haig A Eskandarian
Thomas G Bernhardt
Funding
National Institutes of Health (U19 AI107774)
- Thomas R Ioerger
- Eric J Rubin
National Institutes of Health (R01 GM76710)
- Suzanne Walker
National Institutes of Health (R01AI083365)
- Thomas G Bernhardt
National Institutes of Health (F32GM123579)
- Michael A Welsh
Swiss National Science Foundation (205321_134786)
- Georg E Fantner
Innovative Medicines Initiative (115337)
- John McKinney
EU-FP7/Eurostars (E!8213)
- Georg E Fantner
European Molecular Biology Organization (750-2016)
- Haig A Eskandarian
National Science Foundation (DGE0946799)
- Karen J Kieser
National Institutes of Health (U19AI109764)
- Thomas G Bernhardt
Swiss National Science Foundation (205320_152675)
- Georg E Fantner
Burroughs Wellcome Fund (Career Award at the Scientific Interface)
- E Hesper Rego
American Heart Association (14POST18480014)
- Lok-To Sham
Simons Foundation (Fellow of the Life Sciences Research Foundation Award)
- Hoong C Lim
Swiss National Science Foundation (310030_156945)
- John McKinney
European Union (FP7/2007-2013/ERC Grant agreement No. 307338 (NaMic))
- Georg E Fantner
European Molecular Biology Organization (191-2014)
- Haig A Eskandarian
National Science Foundation (DGE1144152)
- Karen J Kieser
National Institutes of Health (F32AI104287)
- E Hesper Rego
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Bavesh D Kana, University of the Witwatersrand, South Africa
Version history
- Received: April 12, 2018
- Accepted: October 11, 2018
- Accepted Manuscript published: October 16, 2018 (version 1)
- Version of Record published: November 12, 2018 (version 2)
- Version of Record updated: September 5, 2019 (version 3)
Copyright
© 2018, Baranowski et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Maturing Mycobacterium smegmatis peptidoglycan requires non-canonical crosslinks to maintain shape
eLife 7:e37516.
https://doi.org/10.7554/eLife.37516
Further reading
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- Epidemiology and Global Health
- Microbiology and Infectious Disease
A better understanding of the mechanisms underpinning the growth of mycobacteria could help identify targets for new antibiotics.
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- Microbiology and Infectious Disease
In the Firmicutes phylum, GpsB is a membrane associated protein that coordinates peptidoglycan synthesis with cell growth and division. Although GpsB has been studied in several bacteria, the structure, function, and interactome of Staphylococcus aureus GpsB is largely uncharacterized. To address this knowledge gap, we solved the crystal structure of the N-terminal domain of S. aureus GpsB, which adopts an atypical, asymmetric dimer, and demonstrates major conformational flexibility that can be mapped to a hinge region formed by a three-residue insertion exclusive to Staphylococci. When this three-residue insertion is excised, its thermal stability increases, and the mutant no longer produces a previously reported lethal phenotype when overexpressed in Bacillus subtilis. In S. aureus, we show that these hinge mutants are less functional and speculate that the conformational flexibility imparted by the hinge region may serve as a dynamic switch to fine-tune the function of the GpsB complex and/or to promote interaction with its various partners. Furthermore, we provide the first biochemical, biophysical, and crystallographic evidence that the N-terminal domain of GpsB binds not only PBP4, but also FtsZ, through a conserved recognition motif located on their C-termini, thus coupling peptidoglycan synthesis to cell division. Taken together, the unique structure of S. aureus GpsB and its direct interaction with FtsZ/PBP4 provide deeper insight into the central role of GpsB in S. aureus cell division.
