scholarly journals A unique class of Zn2+-binding PBPs underlies cephalosporin resistance and sporogenesis in Clostridioides difficile

2022 ◽  
Author(s):  
Michael D Sacco ◽  
Shaohui Wang ◽  
Swamy R Adapa ◽  
Xiujun Zhang ◽  
Maura V Gongora ◽  
...  
Keyword(s):  
Cell Wall ◽  
Conformational Changes ◽  
Extreme Environments ◽  
Binding Motif ◽  
Antibiotic Development ◽  
Clostridioides Difficile ◽  
Wide Range ◽  
Cephalosporin Resistance ◽  
And Function ◽  
Hospital Acquired

β-Lactam antibiotics, particularly cephalosporins, are major risk factors for C. difficile infection (CDI), the most common hospital acquired infection. These broad-spectrum antibiotics irreversibly inhibit penicillin-binding proteins (PBPs), essential enzymes that assemble the bacterial cell wall. Little is known about the C. difficile PBPs, yet they play central roles in the growth, infection, and transmission of this pathogen. In this study we discover that PBP2, essential for vegetative growth, is the primary bactericidal target for β-lactams in C. difficile. We further demonstrate PBP2 is insensitive to cephalosporin inhibition, revealing a key cause of the well-documented, but poorly understood, cephalosporin resistance in C. difficile. For the first time, we determine the crystal structures of C. difficile PBP2, which bears several highly unique features, including significant ligand-induced conformational changes and an active site Zn2+-binding motif that influences β-lactam binding and protein stability. Remarkably, this motif is shared in two other C. difficile PBPs essential for sporulation, PBP3 and SpoVD. While these PBPs are present in a wide range of bacterial taxa, including species in extreme environments and the human gut, they are mostly found in anaerobes, typically Firmicutes. The widespread presence of this convergently evolved thiol-containing motif and its cognate Zn2+ suggests it may function as a redox-sensor to regulate cell wall synthesis for survival in adverse environments. Collectively, our findings address important etiological questions surrounding C. difficile, characterize new elements of PBP structure and function, and lay the groundwork for antibiotic development targeting both C. difficile growth and sporulation.

Influence of Calcium Ions on the Plant Cell Surface: Membrane Fusions and Conformational Changes

1974 ◽  
Vol 32 ◽  
pp. 154-155
Author(s):  
D. James Morré ◽  
Charles E. Bracker ◽  
William J. VanDerWoude
Keyword(s):  
Cell Wall ◽  
Cell Surface ◽  
Conformational Changes ◽  
Calcium Ions ◽  
Surface Membrane ◽  
Carboxyl Groups ◽  
Cross Linking ◽  
Ultrastructural Evidence ◽  
Glycine Max L ◽  
Wall Extensibility

Calcium ions in the concentration range 5-100 mM inhibit auxin-induced cell elongation and wall extensibility of plant stems. Inhibition of wall extensibility requires that the tissue be living; growth inhibition cannot be explained on the basis of cross-linking of carboxyl groups of cell wall uronides by calcium ions. In this study, ultrastructural evidence was sought for an interaction of calcium ions with some component other than the wall at the cell surface of soybean (Glycine max (L.) Merr.) hypocotyls.

Chaperonin as the normal controls and pathological anti-stress response in the human reproductive system

2016 ◽  
pp. 126-129
Author(s):  
M. Makarenko ◽  
◽  
D. Hovsyeyev ◽  
L. Sydoryk ◽  
◽  
...  
Keyword(s):  
Reproductive System ◽  
Stress Proteins ◽  
Physiological Stress ◽  
Protein Complexes ◽  
Reproductive Function ◽  
Intercellular Signaling ◽  
Toll Like Receptors ◽  
Wide Range ◽  
Protein Functions ◽  
And Function

Different kinds of physiological stress cause mass changes in the cells, including the changes in the structure and function of the protein complexes and in separate molecules. The protein functions is determined by its folding (the spatial conclusion), which depends on the functioning of proteins of thermal shock- molecular chaperons (HSPs) or depends on the stress proteins, that are high-conservative; specialized proteins that are responsible for the correct proteinaceous folding. The family of the molecular chaperones/ chaperonins/ Hsp60 has a special place due to the its unique properties of activating the signaling cascades through the system of Toll-like receptors; it also stimulates the cells to produce anti- inflammatory cytokines, defensins, molecules of cell adhesion and the molecules of MHC; it functions as the intercellular signaling molecule. The pathological role of Hsp60 is established in a wide range of illnesses, from diabetes to atherosclerosis, where Hsp60 takes part in the regulation of both apoptosis and the autoimmune processes. The presence of the HSPs was found in different tissues that are related to the reproductive system. Key words: molecular chaperons (HSPs), Toll-like receptors, reproductive function, natural auto antibody.

Possession and Repetition

2012 ◽  
Vol 6 (1-3) ◽  
pp. 243-259 ◽  
Author(s):  
Yohan Yoo
Keyword(s):  
First Century ◽  
Daily Lives ◽  
Modern Times ◽  
Sacred Texts ◽  
New Methods ◽  
Wide Range ◽  
Lay Buddhists ◽  
Iconic Status ◽  
And Function ◽  
To Receive

This article demonstrates the need for the iconic status and function of Buddhist scripture to receive more attention by illuminating how lay Korean Buddhists try to appropriate the power of sutras. The oral and aural aspects of scripture, explained by Wilfred Cantwell Smith, provide only a limited understanding of the characteristics of scripture. It should be noted that, before modern times, most lay people, not only in Buddhist cultures but also in Christian and other traditions, neither had the chance to recite scriptures nor to listen to their recitations regularly. Several clear examples demonstrate contemporary Korean Buddhists’ acceptance of the iconic status of sutras and their attempt to appropriate the power and status of those sacred texts. In contemporary Korea, lay Buddhists try to claim the power of scriptures in their daily lives by repeating and possessing them. Twenty-first century lay believers who cannot read or recite in a traditional style have found new methods of repetition, such as internet programs for copying sacred texts and for playing recordings of their recitations. In addition, many Korean Buddhists consider the act of having sutras in one’s possession to be an effective way of accessing the sacred status and power of these texts. Hence, various ways of possessing them have been developed in a wide range of products, from fancy gilded sutras to sneakers embroidered with mantras.

Constant pH Molecular Dynamics Reveals How Proton Release Drives the Conformational Transition of a Transmembrane Efflux Pump

2017 ◽  
Author(s):  
Jana Shen ◽  
Zhi Yue ◽  
Helen Zgurskaya ◽  
Wei Chen
Keyword(s):  
Molecular Dynamics ◽  
Conformational Changes ◽  
Transmembrane Domain ◽  
Conformational Transition ◽  
Conformational Dynamics ◽  
Proton Release ◽  
Intrinsic Resistance ◽  
Constant Ph ◽  
Wide Range ◽  
Constant Ph Molecular Dynamics

AcrB is the inner-membrane transporter of E. coli AcrAB-TolC tripartite efflux complex, which plays a major role in the intrinsic resistance to clinically important antibiotics. AcrB pumps a wide range of toxic substrates by utilizing the proton gradient between periplasm and cytoplasm. Crystal structures of AcrB revealed three distinct conformational states of the transport cycle, substrate access, binding and extrusion, or loose (L), tight (T) and open (O) states. However, the specific residue(s) responsible for proton binding/release and the mechanism of proton-coupled conformational cycling remain controversial. Here we use the newly developed membrane hybrid-solvent continuous constant pH molecular dynamics technique to explore the protonation states and conformational dynamics of the transmembrane domain of AcrB. Simulations show that both Asp407 and Asp408 are deprotonated in the L/T states, while only Asp408 is protonated in the O state. Remarkably, release of a proton from Asp408 in the O state results in large conformational changes, such as the lateral and vertical movement of transmembrane helices as well as the salt-bridge formation between Asp408 and Lys940 and other sidechain rearrangements among essential residues.Consistent with the crystallographic differences between the O and L protomers, simulations offer dynamic details of how proton release drives the O-to-L transition in AcrB and address the controversy regarding the proton/drug stoichiometry. This work offers a significant step towards characterizing the complete cycle of proton-coupled drug transport in AcrB and further validates the membrane hybrid-solvent CpHMD technique for studies of proton-coupled transmembrane proteins which are currently poorly understood. <p><br></p>

pH-Dependent Thermal Stability of Vibrio cholerae L-asparaginase

2019 ◽  
Vol 26 (10) ◽  
pp. 743-750 ◽  
Author(s):  
Remya Radha ◽  
Sathyanarayana N. Gummadi
Keyword(s):  
Vibrio Cholerae ◽  
Conformational Changes ◽  
Kinetic Studies ◽  
Structural Features ◽  
Structure Stability ◽  
Kcal Mole ◽  
Scanning Calorimetry ◽  
Wide Range ◽  
Ph Dependent ◽  
Ph Range

Background:pH is one of the decisive macromolecular properties of proteins that significantly affects enzyme structure, stability and reaction rate. Change in pH may protonate or deprotonate the side group of aminoacid residues in the protein, thereby resulting in changes in chemical and structural features. Hence studies on the kinetics of enzyme deactivation by pH are important for assessing the bio-functionality of industrial enzymes. L-asparaginase is one such important enzyme that has potent applications in cancer therapy and food industry.Objective:The objective of the study is to understand and analyze the influence of pH on deactivation and stability of Vibrio cholerae L-asparaginase.Methods:Kinetic studies were conducted to analyze the effect of pH on stability and deactivation of Vibrio cholerae L-asparaginase. Circular Dichroism (CD) and Differential Scanning Calorimetry (DSC) studies have been carried out to understand the pH-dependent conformational changes in the secondary structure of V. cholerae L-asparaginase.Results:The enzyme was found to be least stable at extreme acidic conditions (pH< 4.5) and exhibited a gradual increase in melting temperature from 40 to 81 °C within pH range of 4.0 to 7.0. Thermodynamic properties of protein were estimated and at pH 7.0 the protein exhibited ΔG37of 26.31 kcal mole-1, ΔH of 204.27 kcal mole-1 and ΔS of 574.06 cal mole-1 K-1.Conclusion:The stability and thermodynamic analysis revealed that V. cholerae L-asparaginase was highly stable over a wide range of pH, with the highest stability in the pH range of 5.0–7.0.

Influence of Ascorbic Acid on the Structure and Function of Alpha-2- macroglobulin: Investigations using Spectroscopic and Thermodynamic Techniques

2020 ◽  
Vol 27 (3) ◽  
pp. 201-209
Author(s):  
Syed Saqib Ali ◽  
Mohammad Khalid Zia ◽  
Tooba Siddiqui ◽  
Haseeb Ahsan ◽  
Fahim Halim Khan
Keyword(s):  
Ascorbic Acid ◽  
Conformational Changes ◽  
Structural Changes ◽  
The Body ◽  
Titration Calorimetry ◽  
Spectroscopic Techniques ◽  
Human Beings ◽  
Plasma Ascorbic Acid ◽  
Dietary Antioxidant ◽  
And Function

Background: Ascorbic acid is a classic dietary antioxidant which plays an important role in the body of human beings. It is commonly found in various foods as well as taken as dietary supplement. Objective: The plasma ascorbic acid concentration may range from low, as in chronic or acute oxidative stress to high if delivered intravenously during cancer treatment. Sheep alpha-2- macroglobulin (α2M), a human α2M homologue is a large tetrameric glycoprotein of 630 kDa with antiproteinase activity, found in sheep’s blood. Methods: In the present study, the interaction of ascorbic acid with alpha-2-macroglobulin was explored in the presence of visible light by utilizing various spectroscopic techniques and isothermal titration calorimetry (ITC). Results: UV-vis and fluorescence spectroscopy suggests the formation of a complex between ascorbic acid and α2M apparent by increased absorbance and decreased fluorescence. Secondary structural changes in the α2M were investigated by CD and FT-IR spectroscopy. Our findings suggest the induction of subtle conformational changes in α2M induced by ascorbic acid. Thermodynamics signatures of ascorbic acid and α2M interaction indicate that the binding is an enthalpy-driven process. Conclusion: It is possible that ascorbic acid binds and compromises antiproteinase activity of α2M by inducing changes in the secondary structure of the protein.

The Art of Love Poetry

2018 ◽  
Author(s):  
Erik Gray
Keyword(s):  
Popular Culture ◽  
Cultural History ◽  
Literary Tradition ◽  
Love Poetry ◽  
Erotic Love ◽  
Wide Range ◽  
History Of ◽  
And Function ◽  
Meaning And Function ◽  
Comprehensive History

Love begets poetry; poetry begets love. These two propositions have seemed evident to thinkers and poets across the Western literary tradition. Plato writes that “anyone that love touches instantly becomes a poet.” And even today, when poetry has largely disappeared from the mainstream of popular culture, it retains its romantic associations. But why should this be so—what are the connections between poetry and erotic love that lead us to associate them so strongly with one another? An examination of different theories of both love and poetry across the centuries reveals that the connection between them is not merely an accident of cultural history—the result of our having grown up hearing, or hearing about, love poetry—but something more intrinsic. Even as definitions of them have changed, the two phenomena have consistently been described in parallel terms. Love is characterized by paradox. Above all, it is both necessarily public, because interpersonal, and intensely private; hence it both requires expression and resists it. In poetry, especially lyric poetry, which features its own characteristic paradoxes and silences, love finds a natural outlet. This study considers both the theories and the love poems themselves, bringing together a wide range of examples from different eras in order to examine the major structures that love and poetry share. It does not aim to be a comprehensive history of Western love poetry, but an investigation into the meaning and function of recurrent tropes, forms, and images employed by poets to express and describe erotic love.

scholarly journals TOWARDS FUNCTIONAL ARCHITECTURAL DECOMPOSITION OF CONSTRAINED LAYER INFLATABLE SYSTEMS

2021 ◽  
Vol 1 ◽  
pp. 3219-3228
Author(s):  
Koray Benli ◽  
Jonathan Luntz ◽  
Diann Brei ◽  
Wonhee Kim ◽  
Paul Alexander ◽  
...  
Keyword(s):  
Conceptual Design ◽  
Form And Function ◽  
New Concepts ◽  
Wide Range ◽  
Systematic Understanding ◽  
And Function

AbstractPneumatically activated systems enable myriad types of highly functional inflatables employing a wide range of architectural approaches affecting their form and function, making systematic conceptual design difficult. A new architectural class of pneumatically activated systems, constrained layer inflatable systems, consists of hierarchically architected flat layers of thin airtight bladders that are internally and/or externally constrained to generate a variety of functionalities. The highly hierarchical architectural structure of constrained layer inflatable systems coincides with the hierarchy of produced functions, providing an opportunity for the development of a functional architectural decomposition, capturing the inherent relationship between architectural and functional hierarchies. The basis of the approach is conveyed through the design of an example constrained layer inflatable system. This approach empowers the systematic understanding of the interrelated architectural and functional breakdown of constrained layer inflatable systems, enabling designers to iteratively analyze, synthesize, and re-synthesize the components of the system improving existing designs and exploring new concepts.

scholarly journals 2′FL and LNnT Exert Antipathogenic Effects against C. difficile ATCC 9689 In Vitro, Coinciding with Increased Levels of Bifidobacteriaceae and/or Secondary Bile Acids

Pathogens ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 927
Author(s):  
Louise Kristine Vigsnaes ◽  
Jonas Ghyselinck ◽  
Pieter Van den Van den Abbeele ◽  
Bruce McConnell ◽  
Frédéric Moens ◽  
...  
Keyword(s):  
Antimicrobial Effect ◽  
Secondary Bile Acid ◽  
Clostridioides Difficile ◽  
Life Threatening ◽  
Intermediate Time ◽  
Indigenous Microbiota ◽  
Hospital Acquired ◽  
Gut Microbial Community ◽  
Secondary Bile Acids

Clostridioides difficile (formerly Clostridium difficile) infection (CDI) is one of the most common hospital-acquired infections, which is often triggered by a dysbiosed indigenous gut microbiota (e.g., upon antibiotic therapy). Symptoms can be as severe as life-threatening colitis. The current study assessed the antipathogenic potential of human milk oligosaccharides (HMOs), i.e., 2′-O-fucosyllactose (2′FL), lacto-N-neotetraose (LNnT), and a combination thereof (MIX), against C. difficile ATCC 9689 using in vitro gut models that allowed the evaluation of both direct and, upon microbiota modulation, indirect effects. During a first 48 h fecal batch study, dysbiosis and CDI were induced by dilution of the fecal inoculum. For each of the three donors tested, C. difficile levels strongly decreased (with >4 log CFU/mL) upon treatment with 2′FL, LNnT and MIX versus untreated blanks, coinciding with increased acetate/Bifidobacteriaceae levels. Interindividual differences among donors at an intermediate time point suggested that the antimicrobial effect was microbiota-mediated rather than being a direct effect of the HMOs. During a subsequent 11 week study with the PathogutTM model (specific application of the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®)), dysbiosis and CDI were induced by clindamycin (CLI) treatment. Vancomycin (VNC) treatment cured CDI, but the further dysbiosis of the indigenous microbiota likely contributed to CDI recurrence. Upon co-supplementation with VNC, both 2′FL and MIX boosted microbial activity (acetate and to lesser extent propionate/butyrate). Moreover, 2′FL avoided CDI recurrence, potentially because of increased secondary bile acid production. Overall, while not elucidating the exact antipathogenic mechanisms-of-action, the current study highlights the potential of HMOs to combat CDI recurrence, help the gut microbial community recover after antibiotic treatment, and hence counteract the adverse effects of antibiotic therapies.

New insights on Laminaria digitata ultrastructure through combined conventional chemical fixation and cryofixation

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Christos Katsaros ◽  
Sophie Le Panse ◽  
Gillian Milne ◽  
Carl J. Carrano ◽  
Frithjof Christian Küpper
Keyword(s):  
Cell Wall ◽  
General Structure ◽  
Raw Material ◽  
Rocky Shores ◽  
Chemical Fixation ◽  
Laminaria Digitata ◽  
Vegetative Cells ◽  
Biological Studies ◽  
New Findings ◽  
Wide Range

Abstract The objective of the present study is to examine the fine structure of vegetative cells of Laminaria digitata using both chemical fixation and cryofixation. Laminaria digitata was chosen due to its importance as a model organism in a wide range of biological studies, as a keystone species on rocky shores of the North Atlantic, its use of iodide as a unique inorganic antioxidant, and its significance as a raw material for the production of alginate. Details of the fine structural features of vegetative cells are described, with particular emphasis on the differences between the two methods used, i.e. conventional chemical fixation and freeze-fixation. The general structure of the cells was similar to that already described, with minor differences between the different cell types. An intense activity of the Golgi system was found associated with the thick external cell wall, with large dictyosomes from which numerous vesicles and cisternae are released. An interesting type of cisternae was found in the cryofixed material, which was not visible with the chemical fixation. These are elongated structures, in sections appearing tubule-like, close to the external cell wall or to young internal walls. An increased number of these structures was observed near the plasmodesmata of the pit fields. They are similar to the “flat cisternae” found associated with the forming cytokinetic diaphragm of brown algae. Their possible role is discussed. The new findings of this work underline the importance of such combined studies which reveal new data not known until now using the old conventional methods. The main conclusion of the present study is that cryofixation is the method of choice for studying Laminaria cytology by transmission electron microscopy.

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