scholarly journals Identification of potential regulatory domains within the MreC and MreD components of the cell elongation machinery

2021 ◽  
Author(s):  
Patricia D. A. Rohs ◽  
Jeanna M. Qiu ◽  
Grasiela Torres ◽  
Mandy D. Smith ◽  
Elayne M. Fivenson ◽  
...  
Keyword(s):  
Cell Wall ◽  
Ligand Binding ◽  
Cell Shape ◽  
Genetic System ◽  
Binding Pocket ◽  
Dominant Negative ◽  
Wall Structure ◽  
Regulatory Domains ◽  
C Terminus ◽  
Rod System

The bacterial peptidoglycan (PG) cell wall maintains cell shape and prevents osmotic lysis. During growth of rod-shaped cells, PG is incorporated along the cell cylinder by the RodA-PBP2 synthase of the multi-protein Rod system (elongasome). Filaments of the actin-like MreB protein orient synthesis of the new PG material. They are connected to the RodA-PBP2 synthase in part through the RodZ component. MreC and MreD are other conserved components of the system, but their function is not well understood. Amino acid changes in RodA-PBP2 were recently identified that bypass a requirement for MreC and MreD function, suggesting the Mre proteins act as activators of the synthase. To further investigate their function, we developed a genetic strategy to identify dominant-negative alleles of mreC and mreD in Escherichia coli. Residues essential for Rod system function were identified at the junction of two subdomains within MreC and in a predicted ligand-binding pocket of MreD. Additionally, we found that although the proline-rich C-terminal domain of MreC is non-essential, substitutions within this region disrupt its function. Based on these results, we propose that the C-terminus of MreC and the putative ligand-binding domain of MreD play regulatory roles in controlling Rod system activity. IMPORTANCE: Cell shape in bacteria is largely determined by the cell wall structure that surrounds them. The multi-protein machine called the Rod system (elongasome) has long been implicated in rod-shape determination in bacilli. However, the functions of many of its conserved components remain unclear. Here, we describe a new genetic system to dissect the function of these proteins and how we used it to identify potential regulatory domains within them that may modulate the function of the shape-determining machinery.

Chemical control of plant cell wall structure and of cell shape

1965 ◽  
Vol 161 (985) ◽  
pp. 526-537 ◽  
Keyword(s):  
Cell Wall ◽  
Elastic Properties ◽  
Cell Shape ◽  
Plant Cell Wall ◽  
Sucrose Solution ◽  
Longitudinal Axis ◽  
Cell Wall Structure ◽  
Cellulose Microfibrils ◽  
Wall Structure ◽  
Cortical Cells

It has been shown by Galston, Baker & King (1953) that, if sub-apical sections of pea epicotyl are floated on a sucrose solution containing an appropriate indole acetic acid ( IAA ) concentration, the sections will elongate considerably. If benzimidazole (BIA) is added in addition to the auxin there is a narrow concentration range of BIA over which elongation is strongly inhibited, while increase in section diameter is actually enhanced. This increase in diameter is due specifically to an increase in diameter of the cortical cells. It is shown in this paper that the cortical cells in tissues which have been induced to increase in diameter have a different wall structure from cortical cells in tissues which have increased mainly in length. In the latter case the cellulose microfibrils are arranged transversely to the longitudinal axis of the cell, but, in cells which have increased mainly in diameter, there are two distinct microfibrillar components: a transverse set of microfibrils, and organized bands of longitudinally oriented microfibrils on the outside of the cell wall. The structure of the wall and its plastic and elastic properties are discussed in relation to the way in which the wall may determine the shape of the cell. It is pointed out that changes in cell shape which result from alteration of the chemical environment of the cell could be explained by modification of the plastic and elastic properties of the wall due to change in wall structure. This hypothesis supports the idea that plasticity of the cell wall is an important factor in extension growth and also suggests that the arrangement of microfibrils plays an important part in determining the shape of the cell. If this hypothesis is correct it may have considerable bearing upon the mechanism of cell and tissue differentiation. The observed changes in cell wall structure favour the view that microfibril orientation is controlled through the agency of the protoplasm. The occurrence of bands of longitudinal microfibrils on the outside of the cell wall suggests that cellulose microfibrils can be laid down remote from the cytoplasm.

scholarly journals Probing Dominant Negative Behavior of Glucocorticoid Receptor β through a Hybrid Structural and Biochemical Approach

2018 ◽  
Vol 38 (8) ◽  
pp. e00453-17 ◽  
Author(s):  
Jungki Min ◽  
Lalith Perera ◽  
Juno M. Krahn ◽  
Christine M. Jewell ◽  
Andrea F. Moon ◽  
...  
Keyword(s):  
Glucocorticoid Receptor ◽  
Ligand Binding ◽  
Binding Pocket ◽  
Dominant Negative ◽  
Ru 486 ◽  
Dominant Negative Inhibitor ◽  
Helix 12 ◽  
Binding Energy Analysis ◽  
Biochemical Approach ◽  
Biochemical Analyses

ABSTRACT Glucocorticoid receptor β (GRβ) is associated with glucocorticoid resistance via dominant negative regulation of GRα. To better understand how GRβ functions as a dominant negative inhibitor of GRα at a molecular level, we determined the crystal structure of the ligand binding domain of GRβ complexed with the antagonist RU-486. The structure reveals that GRβ binds RU-486 in the same ligand binding pocket as GRα, and the unique C-terminal amino acids of GRβ are mostly disordered. Binding energy analysis suggests that these C-terminal residues of GRβ do not contribute to RU-486 binding. Intriguingly, the GRβ/RU-486 complex binds corepressor peptide with affinity similar to that of a GRα/RU-486 complex, despite the lack of helix 12. Our biophysical and biochemical analyses reveal that in the presence of RU-486, GRβ is found in a conformation that favors corepressor binding, potentially antagonizing GRα function. This study thus presents an unexpected molecular mechanism by which GRβ could repress transcription.

Bacterial Peptidoglycan Stapling with Functionalized D-Amino Acids

2019 ◽  
Author(s):  
Sylvia L. Rivera ◽  
Akbar Espaillat ◽  
Arjun K. Aditham ◽  
Peyton Shieh ◽  
Chris Muriel-Mundo ◽  
...  
Keyword(s):  
Cell Wall ◽  
Clinical Success ◽  
Bacterial Species ◽  
Enzymatic Reaction ◽  
Amino Acid Derivative ◽  
Wall Structure ◽  
Live Bacteria ◽  
Cross Links ◽  
Osmotic Lysis ◽  
Bacterial Peptidoglycan

Transpeptidation reinforces the structure of cell wall peptidoglycan, an extracellular heteropolymer that protects bacteria from osmotic lysis. The clinical success of transpeptidase-inhibiting β-lactam antibiotics illustrates the essentiality of these cross-linkages for cell wall integrity, but the presence of multiple, seemingly redundant transpeptidases in many bacterial species makes it challenging to determine cross-link function precisely. Here we present a technique to covalently link peptide strands by chemical rather than enzymatic reaction. We employ bio-compatible click chemistry to induce triazole formation between azido- and alkynyl-D-alanine residues that are metabolically installed in the cell walls of Gram-positive and Gram-negative bacteria. Synthetic triazole cross-links can be visualized by substituting azido-D-alanine with azidocoumarin-D-alanine, an amino acid derivative that undergoes fluorescent enhancement upon reaction with terminal alkynes. Cell wall stapling protects the model bacterium Escherichia coli from β-lactam treatment. Chemical control of cell wall structure in live bacteria can provide functional insights that are orthogonal to those obtained by genetics.<br>

Recent Developments in the Downstream Processing of Phycobiliproteins from Algae: A Review

2021 ◽  
Vol 06 ◽  
Author(s):  
Ayekpam Chandralekha Devi ◽  
G. K. Hamsavi ◽  
Simran Sahota ◽  
Rochak Mittal ◽  
Hrishikesh A. Tavanandi ◽  
...  
Keyword(s):  
Cell Wall ◽  
Large Scale ◽  
Downstream Processing ◽  
Review Article ◽  
Current Status ◽  
Wall Structure ◽  
Scale Production ◽  
Cell Wall Disruption ◽  
Recent Developments ◽  
Macro Algae

Abstract: Algae (both micro and macro) have gained huge attention in the recent past for their high commercial value products. They are the source of various biomolecules of commercial applications ranging from nutraceuticals to fuels. Phycobiliproteins are one such high value low volume compounds which are mainly obtained from micro and macro algae. In order to tap the bioresource, a significant amount of work has been carried out for large scale production of algal biomass. However, work on downstream processing aspects of phycobiliproteins (PBPs) from algae is scarce, especially in case of macroalgae. There are several difficulties in cell wall disruption of both micro and macro algae because of their cell wall structure and compositions. At the same time, there are several challenges in the purification of phycobiliproteins. The current review article focuses on the recent developments in downstream processing of phycobiliproteins (mainly phycocyanins and phycoerythrins) from micro and macroalgae. The current status, the recent advancements and potential technologies (that are under development) are summarised in this review article besides providing future directions for the present research area.

scholarly journals A Metzincin and TIMP-Like Protein Pair of a Phage Origin Sensitize Listeria monocytogenes to Phage Lysins and Other Cell Wall Targeting Agents

2021 ◽  
Vol 9 (6) ◽  
pp. 1323
Author(s):  
Etai Boichis ◽  
Nadejda Sigal ◽  
Ilya Borovok ◽  
Anat A. Herskovits
Keyword(s):  
Cell Wall ◽  
Listeria Monocytogenes ◽  
Mammalian Cells ◽  
Protein Pair ◽  
Growth Conditions ◽  
Wall Structure ◽  
Antibiotic Resistant ◽  
Extracellular Milieu ◽  
Virion Release ◽  
Genes Encoding

Infection of mammalian cells by Listeria monocytogenes (Lm) was shown to be facilitated by its phage elements. In a search for additional phage remnants that play a role in Lm’s lifecycle, we identified a conserved locus containing two XRE regulators and a pair of genes encoding a secreted metzincin protease and a lipoprotein structurally similar to a TIMP-family metzincin inhibitor. We found that the XRE regulators act as a classic CI/Cro regulatory switch that regulates the expression of the metzincin and TIMP-like genes under intracellular growth conditions. We established that when these genes are expressed, their products alter Lm morphology and increase its sensitivity to phage mediated lysis, thereby enhancing virion release. Expression of these proteins also sensitized the bacteria to cell wall targeting compounds, implying that they modulate the cell wall structure. Our data indicate that these effects are mediated by the cleavage of the TIMP-like protein by the metzincin, and its subsequent release to the extracellular milieu. While the importance of this locus to Lm pathogenicity remains unclear, the observation that this phage-associated protein pair act upon the bacterial cell wall may hold promise in the field of antibiotic potentiation to combat antibiotic resistant bacterial pathogens.

scholarly journals Probing bacterial cell wall growth by tracing wall-anchored protein complexes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yi-Jen Sun ◽  
Fan Bai ◽  
An-Chi Luo ◽  
Xiang-Yu Zhuang ◽  
Tsai-Shun Lin ◽  
...  
Keyword(s):  
Cell Wall ◽  
Cell Shape ◽  
Bernoulli Shift ◽  
Protein Complexes ◽  
Axial Direction ◽  
Cell Wall Growth ◽  
Flagellar Motors ◽  
Shift Map ◽  
Dynamic Assembly ◽  
Wall Growth

AbstractThe dynamic assembly of the cell wall is key to the maintenance of cell shape during bacterial growth. Here, we present a method for the analysis of Escherichia coli cell wall growth at high spatial and temporal resolution, which is achieved by tracing the movement of fluorescently labeled cell wall-anchored flagellar motors. Using this method, we clearly identify the active and inert zones of cell wall growth during bacterial elongation. Within the active zone, the insertion of newly synthesized peptidoglycan occurs homogeneously in the axial direction without twisting of the cell body. Based on the measured parameters, we formulate a Bernoulli shift map model to predict the partitioning of cell wall-anchored proteins following cell division.

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