Biology subjects

Pohane, A. A.

Publications and source records attributed to Pohane, A. A..

3 recordsLinked to original sources

bioRxiv2021

PplD is a de-N-acetylase of the cell wall linkage unit of streptococcal rhamnopolysaccharides

The cell wall of the human bacterial pathogen Group A Streptococcus (GAS) consists of peptidoglycan decorated with the Lancefield group A carbohydrate (GAC). GAC is a promising target for the development of GAS vaccines. In this study, employing chemical, compositional, and NMR methods, we show that GAC is attached to peptidoglycan via glucosamine 1-phosphate. This structural feature makes the GAC-peptidoglycan linkage highly sensitive to cleavage by nitrous acid and resistant to mild acid conditions. Using this characteristic of the GAS cell wall, we identify PplD as a protein required for deacetylation of linkage N-acetylglucosamine (GlcNAc). X-ray structural analysis indicates that PplD performs catalysis via a modified acid/base mechanism. Genetic surveys in silico together with functional analysis indicate that PplD homologs deacetylate the polysaccharide linkage in many streptococcal species. We further demonstrate that introduction of positive charges to the cell wall by GlcNAc deacetylation protects GAS against host cationic antimicrobial proteins.

microbiology↗

bioRxiv2019

Trehalose recycling promotes energy-efficient mycomembrane reorganization in nutrient-limited mycobacteria

The mycomembrane layer of the mycobacterial cell envelope is a barrier to environmental, immune and antibiotic insults. We find that there is mycomembrane remodeling along the periphery of nutrient-starved, non-replicating mycobacterial cells. Remodeling is supported by recycling of trehalose, a non-mammalian disaccharide that shuttles long-chain mycolate lipids to the mycomembrane. In the absence of trehalose recycling, mycomembrane synthesis continues but mycobacteria experience ATP depletion, enhanced respiration and redox stress. Redox stress from depletion of the trehalose pool is suppressed in a mutant that lacks the OtsAB de novo trehalose synthesis pathway. Our data suggest that trehalose recycling alleviates the energetic burden of mycomembrane remodeling. Loss of trehalose salvage is known to attenuate M. tuberculosis during infection and render the bacterium more susceptible to a variety of drugs. Recycling pathways are emerging targets for sensitizing resource-limited bacterial pathogens to host and antibiotic stress.

microbiology↗

bioRxiv2018

Sidewall cell envelope synthesis and remodeling in pole-growing mycobacteria

O_SCPLOWDC_SCPLOW-amino acid probes label cell wall peptidoglycan at both the poles and sidewall of pole-growing mycobacteria. Since peptidoglycan assembly along the cell periphery could provide a rapid, growth-independent means by which to edit the cell wall, we sought to clarify the precise metabolic fates of these probes. O_SCPLOWDC_SCPLOW-amino acid monopeptides were incorporated into peptidoglycan by O_SCPLOWLC_SCPLOWO_SCPCAP,C_SCPCAPO_SCPLOWDC_SCPLOW-transpeptidase remodeling enzymes to varying extents. Dipeptides were incorporated into cytoplasmic precursors. While dipeptide-marked peptidoglycan synthesis at the poles was associated with cell elongation, synthesis along the periphery was highly responsive to cell wall damage. Our observations suggest a post-expansion role for peptidoglycan assembly along the mycobacterial sidewall and provide a conceptual framework for understanding cell wall robustness in the face of polar growth.

microbiology↗