scholarly journals Esx Systems and the Mycobacterial Cell Envelope: What's the Connection?

2017 ◽  
Vol 199 (17) ◽  
Author(s):  
Rachel E. Bosserman ◽  
Patricia A. Champion
Keyword(s):  
Cell Wall ◽  
Outer Membrane ◽  
Protein Transport ◽  
Cytoplasmic Membrane ◽  
Cell Envelope ◽  
Transport Proteins ◽  
Cell Wall Synthesis ◽  
Mycobacterial Cell ◽  
Genes Encoding ◽  
Associated Proteins

ABSTRACT Mycobacterial 6-kDa early secreted antigenic target (ESAT-6) system (ESX) exporters transport proteins across the cytoplasmic membrane. Many proteins transported by ESX systems are then translocated across the mycobacterial cell envelope and secreted from the cell. Although the mechanism underlying protein transport across the mycolate outer membrane remains elusive, the ESX systems are closely connected with and localize to the cell envelope. Links between ESX-associated proteins, cell wall synthesis, and the maintenance of cell envelope integrity have been reported. Genes encoding the ESX systems and those required for biosynthesis of the mycobacterial envelope are coregulated. Here, we review the interplay between ESX systems and the mycobacterial cell envelope.

scholarly journals Direct Interaction of Polar Scaffolding Protein Wag31 with Nucleoid-Associated Protein Rv3852 Regulates Its Polar Localization

Cells ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 1558
Author(s):  
Rajni Garg ◽  
Chinmay Anand ◽  
Sohini Ganguly ◽  
Sandhya Rao ◽  
Rinkee Verma ◽  
...  
Keyword(s):  
Cell Wall ◽  
Cell Envelope ◽  
Transmembrane Helix ◽  
Ectopic Expression ◽  
Direct Interaction ◽  
Fine Tuning ◽  
Scaffolding Protein ◽  
Physical Interaction ◽  
Cell Wall Synthesis ◽  
Interaction Approach

Rv3852 is a unique nucleoid-associated protein (NAP) found exclusively in Mycobacterium tuberculosis (Mtb) and closely related species. Although annotated as H-NS, we showed previously that it is very different from H-NS in its properties and is distinct from other NAPs, anchoring to cell membrane by virtue of possessing a C-terminal transmembrane helix. Here, we investigated the role of Rv3852 in Mtb in organizing architecture or synthesis machinery of cell wall by protein–protein interaction approach. We demonstrated a direct physical interaction of Rv3852 with Wag31, an important cell shape and cell wall integrity determinant essential in Mtb. Wag31 localizes to the cell poles and possibly acts as a scaffold for cell wall synthesis proteins, resulting in polar cell growth in Mtb. Ectopic expression of Rv3852 in M. smegmatis resulted in its interaction with Wag31 orthologue DivIVAMsm. Binding of the NAP to Wag31 appears to be necessary for fine-tuning Wag31 localization to the cell poles, enabling complex cell wall synthesis in Mtb. In Rv3852 knockout background, Wag31 is mislocalized resulting in disturbed nascent peptidoglycan synthesis, suggesting that the NAP acts as a driver for localization of Wag31 to the cell poles. While this novel association between these two proteins presents one of the mechanisms to structure the elaborate multi-layered cell envelope of Mtb, it also exemplifies a new function for a NAP in mycobacteria.

Sensitivity of normal and mutant strains of Escherichia coli to actinomycin-D

1972 ◽  
Vol 18 (6) ◽  
pp. 909-915 ◽  
Author(s):  
A. P. Singh ◽  
K.-J. Cheng ◽  
J. W. Costerton ◽  
E. S. Idziak ◽  
J. M. Ingram
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Wild Type Strain ◽  
Actinomycin D ◽  
Cytoplasmic Membrane ◽  
Cell Envelope ◽  
Coli Strain ◽  
Wild Type ◽  
Mutant Strains ◽  
In The Wild

The site of the cell barrier to actinomycin-D uptake was studied using a wild-type Escherichia coli strain P and its cell envelope-defective filamentous mutants, strains 6γ and 12γ, both of which 'leak' β-galactosidase and alkaline phosphatase into the medium during growth indicating both membrane and cell-wall defects. Actinomycin-D entered the cells of these two mutant strains as evidenced by the inhibition of both 14C-uracil incorporation and synthesis of the induced β-galactosidase system. Under similar conditions, no inhibition occurred in the wild-type strain and its sucrose-lysozyme prepared spheroplasts. Actinomycin-D did, however, inhibit the above-mentioned systems in the wild-type sucrose-lysozyme spheroplasts prepared in the presence of 2 mM EDTA. The experimental data indicate that although the cell wall may act as a primary barrier or sieve to actinomycin-D, the cytoplasmic membrane should be considered the final and determinative barrier to this antibiotic.

scholarly journals The ColM Family, Polymorphic Toxins Breaching the Bacterial Cell Wall

mBio ◽  
2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Maarten G. K. Ghequire ◽  
Susan K. Buchanan ◽  
René De Mot
Keyword(s):  
Cell Wall ◽  
Bacterial Cell ◽  
Cytoplasmic Membrane ◽  
Catalytic Domain ◽  
Gram Negative Bacteria ◽  
Antibacterial Peptides ◽  
Gram Negative ◽  
Lipid Ii ◽  
Associated Proteins ◽  
Colicin M

ABSTRACT Bacteria host an arsenal of antagonism-mediating molecules to combat for ecologic space. Bacteriocins represent a pivotal group of secreted antibacterial peptides and proteins assisting in this fight, mainly eliminating relatives. Colicin M, a model for peptidoglycan-interfering bacteriocins in Gram-negative bacteria, appears to be part of a set of polymorphic toxins equipped with such a catalytic domain (ColM) targeting lipid II. Diversifying recombination has enabled parasitism of different receptors and has also given rise to hybrid bacteriocins in which ColM is associated with another toxin module. Remarkably, ColM toxins have recruited a diverse array of immunity partners, comprising cytoplasmic membrane-associated proteins with different topologies. Together, these findings suggest that different immunity mechanisms have evolved for ColM, in contrast to bacteriocins with nuclease activities.

scholarly journals MmpL3 is a lipid transporter that binds trehalose monomycolate and phosphatidylethanolamine

2019 ◽  
Vol 116 (23) ◽  
pp. 11241-11246 ◽  
Author(s):  
Chih-Chia Su ◽  
Philip A. Klenotic ◽  
Jani Reddy Bolla ◽  
Georgiana E. Purdy ◽  
Carol V. Robinson ◽  
...  
Keyword(s):  
Cell Wall ◽  
Cell Envelope ◽  
Native Mass Spectrometry ◽  
Mycolic Acids ◽  
Mycobacterial Cell ◽  
Exact Function ◽  
Species Specific ◽  
Mycobacterial Cell Wall ◽  
Trehalose Monomycolate ◽  
Lipid Transporter

The cell envelope ofMycobacterium tuberculosisis notable for the abundance of mycolic acids (MAs), essential to mycobacterial viability, and of other species-specific lipids. The mycobacterial cell envelope is extremely hydrophobic, which contributes to virulence and antibiotic resistance. However, exactly how fatty acids and lipidic elements are transported across the cell envelope for cell-wall biosynthesis is unclear. Mycobacterial membrane protein Large 3 (MmpL3) is essential and required for transport of trehalose monomycolates (TMMs), precursors of MA-containing trehalose dimycolates (TDM) and mycolyl arabinogalactan peptidoglycan, but the exact function of MmpL3 remains elusive. Here, we report a crystal structure ofMycobacterium smegmatisMmpL3 at a resolution of 2.59 Å, revealing a monomeric molecule that is structurally distinct from all known bacterial membrane proteins. A previously unknown MmpL3 ligand, phosphatidylethanolamine (PE), was discovered inside this transporter. We also show, via native mass spectrometry, that MmpL3 specifically binds both TMM and PE, but not TDM, in the micromolar range. These observations provide insight into the function of MmpL3 and suggest a possible role for this protein in shuttling a variety of lipids to strengthen the mycobacterial cell wall.

scholarly journals Identification of Genes Encoding Exported Mycobacterium tuberculosis Proteins Using a Tn552′phoA In Vitro Transposition System

2000 ◽  
Vol 182 (10) ◽  
pp. 2732-2740 ◽  
Author(s):  
Miriam Braunstein ◽  
Thomas J. Griffin ◽  
Jordan I. Kriakov ◽  
Sarah T. Friedman ◽  
Nigel D. F. Grindley ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Protective Immunity ◽  
Cell Envelope ◽  
Open Reading Frames ◽  
Signal Peptides ◽  
Genomic Libraries ◽  
Target Dna ◽  
Genes Encoding ◽  
Associated Proteins

ABSTRACT Secreted and cell envelope-associated proteins are important to both Mycobacterium tuberculosis pathogenesis and the generation of protective immunity to M. tuberculosis. We used an in vitro Tn552′phoA transposition system to identify exported proteins of M. tuberculosis. The system is simple and efficient, and the transposon inserts randomly into target DNA. M. tuberculosis genomic libraries were targeted with Tn552′phoA transposons, and these libraries were screened in M. smegmatis for active PhoA translational fusions. Thirty-two different M. tuberculosis open reading frames were identified; eight contain standard signal peptides, six contain lipoprotein signal peptides, and seventeen contain one or more transmembrane domains. Four of these proteins had not yet been assigned as exported proteins in the M. tuberculosisdatabases. This collection of exported proteins includes factors that are known to participate in the immune response of M. tuberculosis and proteins with homologies, suggesting a role in pathogenesis. Nine of the proteins appear to be unique to mycobacteria and represent promising candidates for factors that participate in protective immunity and virulence. This technology of creating comprehensive fusion libraries should be applicable to other organisms.

scholarly journals CsiA is a bacterial cell wall synthesis inhibitor contributing to DNA translocation through the cell envelope

2009 ◽  
Vol 72 (3) ◽  
pp. 779-794 ◽  
Author(s):  
Régis Stentz ◽  
Udo Wegmann ◽  
Mary Parker ◽  
Roy Bongaerts ◽  
Laurie Lesaint ◽  
...  
Keyword(s):  
Cell Wall ◽  
Bacterial Cell ◽  
Cell Envelope ◽  
Bacterial Cell Wall ◽  
Cell Wall Synthesis ◽  
Dna Translocation ◽  
Synthesis Inhibitor ◽  
Cell Wall Synthesis Inhibitor

Bactericidal action of peptide antibiotic AS-48 against Escherichia coli K-12

1989 ◽  
Vol 35 (2) ◽  
pp. 318-321 ◽  
Author(s):  
A. Gálvez ◽  
E. Valdivia ◽  
M. Martínez ◽  
M. Maqueda
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Cell Growth ◽  
Mode Of Action ◽  
Cytoplasmic Membrane ◽  
Peptide Antibiotic ◽  
Biosynthetic Pathways ◽  
Bactericidal Action ◽  
Cell Wall Synthesis ◽  
K 12

Peptide antibiotic AS-48 exerts a bactericidal mode of action on exponential cultures of Escherichia coli K-12 through a multi-hit kinetics interaction. AS-48 causes a parallel and gradual cessation of all biosynthetic pathways monitored (protein, RNA, DNA, and cell wall synthesis), the rate of incorporation of labeled precursors, the rate of O2 consumption, and cell growth. These effects have been attributed to alterations of cytoplasmic membrane functions.Key words: Escherichia coli, peptide antibiotic, bactericide.

scholarly journals A cell wall damage response mediated by a sensor kinase/response regulator pair enables beta-lactam tolerance

2015 ◽  
Vol 113 (2) ◽  
pp. 404-409 ◽  
Author(s):  
Tobias Dörr ◽  
Laura Alvarez ◽  
Fernanda Delgado ◽  
Brigid M. Davis ◽  
Felipe Cava ◽  
...  
Keyword(s):  
Cell Wall ◽  
Response Regulator ◽  
Cell Envelope ◽  
Normal Growth ◽  
Cell Diameter ◽  
Cell Wall Synthesis ◽  
Beta Lactam ◽  
Cell Wall Damage ◽  
A Cell

The bacterial cell wall is critical for maintenance of cell shape and survival. Following exposure to antibiotics that target enzymes required for cell wall synthesis, bacteria typically lyse. Although several cell envelope stress response systems have been well described, there is little knowledge of systems that modulate cell wall synthesis in response to cell wall damage, particularly in Gram-negative bacteria. Here we describe WigK/WigR, a histidine kinase/response regulator pair that enablesVibrio cholerae, the cholera pathogen, to survive exposure to antibiotics targeting cell wall synthesis in vitro and during infection. Unlike wild-typeV. cholerae, mutants lackingwigRfail to recover following exposure to cell-wall–acting antibiotics, and they exhibit a drastically increased cell diameter in the absence of such antibiotics. Conversely, overexpression ofwigRleads to cell slimming. Overexpression of activated WigR also results in increased expression of the full set of cell wall synthesis genes and to elevated cell wall content. WigKR-dependent expression of cell wall synthesis genes is induced by various cell-wall–acting antibiotics as well as by overexpression of an endogenous cell wall hydrolase. Thus, WigKR appears to monitor cell wall integrity and to enhance the capacity for increased cell wall production in response to damage. Taken together, these findings implicate WigKR as a regulator of cell wall synthesis that controls cell wall homeostasis in response to antibiotics and likely during normal growth as well.

scholarly journals Exogenous proanthocyanidins improve tolerance of Cu-toxicity by amelioration of oxidative damage and re-programming of gene expression in Medicago sativa

PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0259100
Author(s):  
Siyi Zhao ◽  
Yanqiao Zhu ◽  
Wenwen Liu ◽  
Xiaoshan Wang ◽  
Han Wang ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Cell Wall ◽  
Ascorbic Acid ◽  
Plant Growth ◽  
Medicago Sativa ◽  
Agricultural Practices ◽  
Cell Wall Synthesis ◽  
Genes Encoding ◽  
Stress Damage ◽  
The Impact

Excess copper (Cu) in soil due to industrial and agricultural practices can result in reduced plant growth. Excess Cu resulted in severely retarded root growth with severe discoloration of Alfalfa (Medicago sativa) and Medicago truncatula. Growth in the presence of hydrogen peroxide resulted in similar symptoms that could be partially recovered by the addition of the reductant ascorbic acid revealing damage was likely due to oxidative stress. The addition of proanthocyanidins (PAs) in the presence of Cu prevented much of the damage, including plant growth and restoration of lignin synthesis which was inhibited in the presence of excess Cu. Transcriptome analyses of the impact of excess Cu and the amelioration after PAs treatment revealed that changes were enriched in functions associated with the cell wall and extracellular processes, indicating that inhibition of cell wall synthesis was likely the reason for retarded growth. Excess Cu appeared to induce a strong defense response, along with alterations in the expression of a number of genes encoding transcription factors, notably related to ethylene signaling. The addition of PAs greatly reduced this response, and also induced novel genes that likely help ameliorate the effects of excess Cu. These included induction of genes involved in the last step of ascorbic acid biosynthesis and of enzymes involved in cell wall synthesis. Combined, these results show that excess Cu causes severe oxidative stress damage and inhibition of cell wall synthesis, which can be relieved by the addition of PAs.

scholarly journals Mutational Analysis of the Escherichia coli K-12 TolA N-Terminal Region and Characterization of Its TolQ-Interacting Domain by Genetic Suppression

1998 ◽  
Vol 180 (24) ◽  
pp. 6433-6439 ◽  
Author(s):  
Pierre Germon ◽  
Thierry Clavel ◽  
Anne Vianney ◽  
Raymond Portalier ◽  
Jean Claude Lazzaroni
Keyword(s):  
Escherichia Coli ◽  
Outer Membrane ◽  
Cytoplasmic Membrane ◽  
Transmembrane Domain ◽  
Mutational Analysis ◽  
Cell Envelope ◽  
Transmembrane Helix ◽  
Membrane Integrity ◽  
Genetic Suppression ◽  
K 12

ABSTRACT The Tol-Pal proteins of Escherichia coli are involved in maintaining outer membrane integrity. They form two complexes in the cell envelope. Transmembrane domains of TolQ, TolR, and TolA interact in the cytoplasmic membrane, while TolB and Pal form a complex near the outer membrane. The N-terminal transmembrane domain of TolA anchors the protein to the cytoplasmic membrane and interacts with TolQ and TolR. Extensive mutagenesis of the N-terminal part of TolA was carried out to characterize the residues involved in such processes. Mutations affecting the function of TolA resulted in a lack or an alteration in TolA-TolQ or TolR-TolA interactions but did not affect the formation of TolQ-TolR complexes. Our results confirmed the importance of residues serine 18 and histidine 22, which are part of an SHLS motif highly conserved in the TolA and the related TonB proteins from different organisms. Genetic suppression experiments were performed to restore the functional activity of some tolA mutants. The suppressor mutations all affected the first transmembrane helix of TolQ. These results confirmed the essential role of the transmembrane domain of TolA in triggering interactions with TolQ and TolR.

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