Biology subjects

Cava, f.

Publications and source records attributed to Cava, f..

3 recordsLinked to original sources

bioRxiv2026

Non-canonical peptidoglycan cross-linking is essential for Mycobacterium tuberculosis acid resistance

Mycobacterium tuberculosis withstands acidic conditions to survive and replicate within macrophages. To define the genetic determinants of this adaptation, we performed a transposon screen in a lipid-rich, acidic medium that mimics the host environment and supports robust M. tuberculosis growth. This screen identified ldtB, encoding an L,D-transpeptidase, as essential for growth and survival under acid stress. Loss of LdtB decreased 3-3 peptidoglycan cross-linking, disrupted cell wall architecture, and impaired intrabacterial pH homeostasis, resulting in increased susceptibility to cell wall-active antibiotics. Notably, M. tuberculosis lacking LdtB displayed heightened sensitivity to meropenem within macrophages, suggesting that targeting this enzyme could potentiate {beta}-lactam efficacy during infection. These findings establish LdtB as a key mediator linking peptidoglycan homeostasis to acid stress resistance and underscores the importance of in vitro culture models that recapitulate the host microenvironment for uncovering new in vivo active therapeutic targets. TeaserDisabling a key peptidoglycan cross-linking enzyme compromises M. tuberculosis survival under acidic stress and antibiotic exposure.

microbiology↗

bioRxiv2023

Bacterial cell surface nanoenvironment requires a specialized chaperone to activate a peptidoglycan biosynthetic enzyme

Bacillus subtilis spores are produced inside the cytosol of a mother cell. Spore surface assembly requires the SpoVK protein in the mother cell, but its function is unknown. Here, we report that SpoVK is a dedicated chaperone from a distinct higher-order clade of AAA+ ATPases that activates the peptidoglycan glycosyltransferase MurG during sporulation, even though MurG does not normally require activation by a chaperone during vegetative growth. MurG redeploys to the spore surface during sporulation, where we show that the local pH is reduced and propose that this change in cytosolic nanoenvironment necessitates a specific chaperone for proper MurG function. Further, we show that SpoVK participates in a developmental checkpoint in which improper spore surface assembly inactivates SpoVK, which leads to sporulation arrest. The AAA+ ATPase clade containing SpoVK includes other dedicated chaperones involved in secretion, cell-envelope biosynthesis, and carbohydrate metabolism, suggesting that such fine-tuning might be a widespread feature of different subcellular nanoenvironments.

microbiology↗

bioRxiv2019

Structural basis of peptidoglycan endopeptidase regulation

Most bacteria surround themselves with a cell wall, a strong meshwork consisting primarily of the polymerized aminosugar peptidoglycan (PG). PG is essential for structural maintenance of bacterial cells, and thus for viability. PG is also constantly synthesized and turned over, the latter process is mediated by PG cleavage enzymes, for example the endopeptidases (EPs). EPs themselves are essential for growth, but also promote lethal cell wall degradation after exposure to antibiotics that inhibit PG synthases (e.g., {beta}-lactams). Thus, EPs are attractive targets for novel antibiotics and their adjuvants. However, we have a poor understanding of how these enzymes are regulated in vivo, depriving us of novel pathways for the development of such antibiotics. Here, we have solved crystal structures of the LysM/M23 family peptidase ShyA, the primary EP of the cholera pathogen Vibrio cholerae. Our data suggest that ShyA assumes two drastically different conformations; a more open form that allows for substrate binding, and a closed form, which we predicted to be catalytically inactive. Mutations expected to promote the open conformation caused enhanced activity in vitro and in vivo, and these results were recapitulated in EPs from the divergent pathogens Neisseria gonorrheae and Escherichia coli. Our results suggest that LysM/M23 EPs are regulated via release of the inhibitory Domain1 from the M23 active site, likely through conformational re-arrangement in vivo. SignificanceBacteria digest their cell wall following exposure to antibiotics like penicillin. The endopeptidases (EPs) are among the proteins that catalyze cell wall digestion processes after antibiotic exposure, but we do not understand how these enzymes are regulated during normal growth. Herein, we present the structure of the major EP from the diarrheal pathogen Vibrio cholerae. Surprisingly, we find that EPs from this and other pathogens appear to be produced as a largely inactive precursor that undergoes a conformational shift exposing the active site to engage in cell wall digestion. These results enhance our understanding of how EPs are regulated and could open the door for the development of novel antibiotics that overactivate cell wall digestion processes.

microbiology↗