The penetration of Human Defensin 5 (HD5) through bacterial outer membrane: Simulation studies

2021 ◽  
Author(s):  
Tadsanee Awang ◽  
Prapasiri Pongprayoon
Keyword(s):  
Pathogenic Bacteria ◽  
Lipid A ◽  
Dominant Role ◽  
Membrane Surface ◽  
Innate Immune ◽  
Hydrophobic Core ◽  
Gram Negative ◽  
Head Groups ◽  
Bacterial Outer Membrane ◽  
Human Defensin 5

Abstract Human α-defensin 5 (HD5) is one of cationic antimicrobial peptides which plays a crucial role in an innate immune system in human body. HD5 shows the killing activity against a broad spectrum of pathogenic bacteria by making a pore in a bacterial membrane and penetrating into a cytosol. Nonetheless, its pore-forming mechanisms remain unclear. Thus, in this work, the constant-velocity steered molecular dynamics (SMD) simulation was used to simulate the permeation of a dimeric HD5 into a gram-negative LPS membrane model. Arginine-rich HD5 is found to strongly interact with a LPS surface. Upon arrival, arginines on HD5 interact with lipid A head groups and then drag these charged moieties down into a hydrophobic core resulting in the formation of water-filled pore. Although all arginines are found to interact with a membrane, R13 and R32 appear to play a dominant role in the HD5 adsorption on a gram-negative membrane. Furthermore, one chain of a dimeric HD5 is required for HD5 adhesion. The interactions of arginine-Lipid A head groups play a major role in adhering a cationic HD5 on a membrane surface and retarding a HD5 passage in the meantime.

scholarly journals Flavonoid-membrane Interactions: A Protective Role of Flavonoids at the Membrane Surface?

2005 ◽  
Vol 12 (1) ◽  
pp. 19-25 ◽  
Author(s):  
Patricia I. Oteiza ◽  
Alejandra G. Erlejman ◽  
Sandra V. Verstraeten ◽  
Carl L. Keen ◽  
César G. Fraga
Keyword(s):  
Membrane Surface ◽  
Polar Compounds ◽  
Protective Role ◽  
Membrane Lipid ◽  
Hydrophobic Core ◽  
Head Groups ◽  
Lipid And Protein Oxidation ◽  
Chain Breaking ◽  
A Chain ◽  
And Function

Flavonoids can exert beneficial health effects through multiple mechanisms. In this paper, we address the important, although not fully understood, capacity of flavonoids to interact with cell membranes. The interactions of polyphenols with bilayers include: (a) the partition of the more non-polar compounds in the hydrophobic interior of the membrane, and (b) the formation of hydrogen bonds between the polar head groups of lipids and the more hydrophilic flavonoids at the membrane interface. The consequences of these interactions are discussed. The induction of changes in membrane physical properties can affect the rates of membrane lipid and protein oxidation. The partition of certain flavonoids in the hydrophobic core can result in a chain breaking antioxidant activity. We suggest that interactions of polyphenols at the surface of bilayers through hydrogen bonding, can act to reduce the access of deleterious molecules (i.e. oxidants), thus protecting the structure and function of membranes.

scholarly journals Current Update on Intrinsic and Acquired Colistin Resistance Mechanisms in Bacteria

2021 ◽  
Vol 8 ◽  
Author(s):  
Firdoos Ahmad Gogry ◽  
Mohammad Tahir Siddiqui ◽  
Insha Sultan ◽  
Qazi Mohd. Rizwanul Haq
Keyword(s):  
Pathogenic Bacteria ◽  
Lipid A ◽  
Resistance Mechanisms ◽  
New Drugs ◽  
Resistant Bacteria ◽  
Colistin Resistance ◽  
Gram Negative ◽  
Bacterial Surface ◽  
Resistance Determinants ◽  
Neisseria Meningitides

Colistin regained global interest as a consequence of the rising prevalence of multidrug-resistant Gram-negative Enterobacteriaceae. In parallel, colistin-resistant bacteria emerged in response to the unregulated use of this antibiotic. However, some Gram-negative species are intrinsically resistant to colistin activity, such as Neisseria meningitides, Burkholderia species, and Proteus mirabilis. Most identified colistin resistance usually involves modulation of lipid A that decreases or removes early charge-based interaction with colistin through up-regulation of multistep capsular polysaccharide expression. The membrane modifications occur by the addition of cationic phosphoethanolamine (pEtN) or 4-amino-l-arabinose on lipid A that results in decrease in the negative charge on the bacterial surface. Therefore, electrostatic interaction between polycationic colistin and lipopolysaccharide (LPS) is halted. It has been reported that these modifications on the bacterial surface occur due to overexpression of chromosomally mediated two-component system genes (PmrAB and PhoPQ) and mutation in lipid A biosynthesis genes that result in loss of the ability to produce lipid A and consequently LPS chain, thereafter recently identified variants of plasmid-borne genes (mcr-1 to mcr-10). It was hypothesized that mcr genes derived from intrinsically resistant environmental bacteria that carried chromosomal pmrC gene, a part of the pmrCAB operon, code three proteins viz. pEtN response regulator PmrA, sensor kinase protein PmrAB, and phosphotransferase PmrC. These plasmid-borne mcr genes become a serious concern as they assist in the dissemination of colistin resistance to other pathogenic bacteria. This review presents the progress of multiple strategies of colistin resistance mechanisms in bacteria, mainly focusing on surface changes of the outer membrane LPS structure and other resistance genetic determinants. New handier and versatile methods have been discussed for rapid detection of colistin resistance determinants and the latest approaches to revert colistin resistance that include the use of new drugs, drug combinations and inhibitors. Indeed, more investigations are required to identify the exact role of different colistin resistance determinants that will aid in developing new less toxic and potent drugs to treat bacterial infections. Therefore, colistin resistance should be considered a severe medical issue requiring multisectoral research with proper surveillance and suitable monitoring systems to report the dissemination rate of these resistant genes.

scholarly journals Antimicrobial Peptide Potency is Facilitated by Greater Conformational Flexibility when Binding to Gram-negative Bacterial Inner Membranes

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Sarah-Beth T. A. Amos ◽  
Louic S. Vermeer ◽  
Philip M. Ferguson ◽  
Justyna Kozlowska ◽  
Matthew Davy ◽  
...  
Keyword(s):  
Membrane Surface ◽  
Conformational Flexibility ◽  
Gram Negative Bacteria ◽  
Hydrophobic Core ◽  
Inner Membrane ◽  
Membrane Interaction ◽  
Gram Negative ◽  
Bacterial Membranes ◽  
Self Association ◽  
Dynamics Simulations

Abstract The interaction of antimicrobial peptides (AMPs) with the inner membrane of Gram-negative bacteria is a key determinant of their abilities to exert diverse bactericidal effects. Here we present a molecular level understanding of the initial target membrane interaction for two cationic α-helical AMPs that share structural similarities but have a ten-fold difference in antibacterial potency towards Gram-negative bacteria. The binding and insertion from solution of pleurocidin or magainin 2 to membranes representing the inner membrane of Gram-negative bacteria, comprising a mixture of 128 anionic and 384 zwitterionic lipids, is monitored over 100 ns in all atom molecular dynamics simulations. The effects of the membrane interaction on both the peptide and lipid constituents are considered and compared with new and published experimental data obtained in the steady state. While both magainin 2 and pleurocidin are capable of disrupting bacterial membranes, the greater potency of pleurocidin is linked to its ability to penetrate within the bacterial cell. We show that pleurocidin displays much greater conformational flexibility when compared with magainin 2, resists self-association at the membrane surface and penetrates further into the hydrophobic core of the lipid bilayer. Conformational flexibility is therefore revealed as a key feature required of apparently α-helical cationic AMPs for enhanced antibacterial potency.

scholarly journals Cationic Hydrophobic Peptides with Antimicrobial Activity

2002 ◽  
Vol 46 (11) ◽  
pp. 3585-3590 ◽  
Author(s):  
Margareta Stark ◽  
Li-Ping Liu ◽  
Charles M. Deber
Keyword(s):  
Antimicrobial Activity ◽  
Membrane Surface ◽  
Threshold Value ◽  
Bacterial Membrane ◽  
Hydrophobic Core ◽  
Anionic Phospholipid ◽  
Bacterial Membranes ◽  
Gram Positive Bacteria ◽  
Hydrophobic Peptides ◽  
Head Groups

ABSTRACT The MICs of cationic, hydrophobic peptides of the prototypic sequence KKAAAXAAAAAXAAWAAXAAAKKKK-amide (where X is one of the 20 commonly occurring amino acids) are in a low micromolar range for a panel of gram-negative and gram-positive bacteria, with no or low hemolytic activity against human and rabbit erythrocytes. The peptides are active only when the average segmental hydrophobicity of the 19-residue core is above an experimentally determined threshold value (where X is Phe, Trp, Leu, Ile, Met, Val, Cys, or Ala). Antimicrobial activity could be increased by using peptides that were truncated from the prototype length to 11 core residues, with X being Phe and with 6 Lys residues grouped at the N terminus. We propose a mechanism for the interaction between these peptides and bacterial membranes similar to the “carpet model,” wherein the Lys residues interact with the anionic phospholipid head groups in the bacterial membrane surface and the hydrophobic core portion of the peptide is then able to interact with the lipid bilayer, causing disruption of the bacterial membrane.

scholarly journals The Lipid A Phosphate Position Determines Differential Host Toll-Like Receptor 4 Responses to Phylogenetically Related Symbiotic and Pathogenic Bacteria

2010 ◽  
Vol 79 (1) ◽  
pp. 203-210 ◽  
Author(s):  
Stephen R. Coats ◽  
Alex B. Berezow ◽  
Thao T. To ◽  
Sumita Jain ◽  
Brian W. Bainbridge ◽  
...  
Keyword(s):  
Pathogenic Bacteria ◽  
Lipid A ◽  
Specific Capacity ◽  
Immune Defense ◽  
Innate Immune ◽  
Toll Like Receptor ◽  
Critical Aspect ◽  
Toll Like Receptor 4 ◽  
Differential Host ◽  
The Relationship

ABSTRACTThe human symbiontBacteroides thetaiotaomicronpromotes intestinal function and health, whereas the phylogenetically related pathogenPorphyromonas gingivalisis associated with the chronic oral inflammatory disease periodontitis. Although bothB. thetaiotaomicronandP. gingivalissynthesize lipopolysaccharides (LPS) consisting of penta-acylated, monophosphorylated lipid A in addition to immunologically silent, nonphosphorylated lipid A, they elicit strikingly distinct Toll-like receptor 4 (TLR4) responses. We show that the phosphate position of penta-acylated, monophosphorylated lipid A is a key feature for determining the differential TLR4 responses elicited by these evolutionarily related bacteria.B. thetaiotaomicronproduces TLR4-stimulatory lipid A bearing a 1-phosphate, in contrast toP. gingivalis, which produces TLR4-evasive lipid A bearing a 4′-phosphate. Confirming these observations, recombinantEscherichia coliLPS containing penta-acylated, 1-phosphorylated lipid A is more TLR4 stimulatory than LPS containing 4′-phosphorylated lipid A. The specific capacity of a Gram-negative bacterium to alert or evade the host innate immune defense system through TLR4-dependent signaling is currently recognized as a critical aspect defining the relationship between the host and the bacterium. We propose that the distinct lipid A phosphate positions observed for theB. thetaiotaomicronandP. gingivalisLPS contributes to the manifestation of these bacteria as commensal or pathogen within the human host.

scholarly journals Asymmetric phospholipid: lipopolysaccharide bilayers; a Gram-negative bacterial outer membrane mimic

2013 ◽  
Vol 10 (89) ◽  
pp. 20130810 ◽  
Author(s):  
Luke A. Clifton ◽  
Maximilian W. A. Skoda ◽  
Emma L. Daulton ◽  
Arwel V. Hughes ◽  
Anton P. Le Brun ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Lipid A ◽  
Membrane Dynamics ◽  
Gram Negative ◽  
Outer Leaflet ◽  
Physical Study ◽  
Bacterial Outer Membrane ◽  
Membrane Models ◽  
Initial Deposition

The Gram-negative bacterial outer membrane (OM) is a complex and highly asymmetric biological barrier but the small size of bacteria has hindered advances in in vivo examination of membrane dynamics. Thus, model OMs, amenable to physical study, are important sources of data. Here, we present data from asymmetric bilayers which emulate the OM and are formed by a simple two-step approach. The bilayers were deposited on an SiO 2 surface by Langmuir–Blodgett deposition of phosphatidylcholine as the inner leaflet and, via Langmuir–Schaefer deposition, an outer leaflet of either Lipid A or Escherichia coli rough lipopolysaccharides (LPS). The membranes were examined using neutron reflectometry (NR) to examine the coverage and mixing of lipids between the bilayer leaflets. NR data showed that in all cases, the initial deposition asymmetry was mostly maintained for more than 16 h. This stability enabled the sizes of the headgroups and bilayer roughness of 1,2-dipalmitoyl- sn -glycero-3-phosphocholine and Lipid A, Rc-LPS and Ra-LPS to be clearly resolved. The results show that rough LPS can be manipulated like phospholipids and used to fabricate advanced asymmetric bacterial membrane models using well-known bilayer deposition techniques. Such models will enable OM dynamics and interactions to be studied under in vivo -like conditions.

An outlook for food sterilization technology: targeting the outer membrane of foodborne gram-negative pathogenic bacteria

2021 ◽  
Vol 42 ◽  
pp. 15-22
Author(s):  
Zhaohuan Zhang ◽  
Zhenhua Huang ◽  
Jinrong Tong ◽  
Qian Wu ◽  
Yingjie Pan ◽  
...  
Keyword(s):  
Outer Membrane ◽  
Pathogenic Bacteria ◽  
Gram Negative ◽  
Food Sterilization

scholarly journals Analyses of Lipid A Diversity in Gram-Negative Intestinal Bacteria Using Liquid Chromatography–Quadrupole Time-of-Flight Mass Spectrometry

Metabolites ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 197
Author(s):  
Nobuyuki Okahashi ◽  
Masahiro Ueda ◽  
Fumio Matsuda ◽  
Makoto Arita
Keyword(s):  
Mass Spectrometry ◽  
Immune Response ◽  
Liquid Chromatography ◽  
Mammalian Cells ◽  
Lipid A ◽  
Acyl Chain ◽  
Time Of Flight ◽  
Intestinal Bacteria ◽  
Gram Negative ◽  
Flight Mass Spectrometry

Lipid A is a characteristic molecule of Gram-negative bacteria that elicits an immune response in mammalian cells. The presence of structurally diverse lipid A types in the human gut bacteria has been suggested before, and this appears associated with the immune response. However, lipid A structures and their quantitative heterogeneity have not been well characterized. In this study, a method of analysis for lipid A using liquid chromatography–quadrupole time-of-flight mass spectrometry (LC-QTOF/MS) was developed and applied to the analyses of Escherichia coli and Bacteroidetes strains. In general, phosphate compounds adsorb on stainless-steel piping and cause peak tailing, but the use of an ammonia-containing alkaline solvent produced sharp lipid A peaks with high sensitivity. The method was applied to E. coli strains, and revealed the accumulation of lipid A with abnormal acyl side chains in knockout strains as well as known diphosphoryl hexa-acylated lipid A in a wild-type strain. The analysis of nine representative strains of Bacteroidetes showed the presence of monophosphoryl penta-acylated lipid A characterized by a highly heterogeneous main acyl chain length. Comparison of the structures and amounts of lipid A among the strains suggested a relationship between lipid A profiles and the phylogenetic classification of the strains.

scholarly journals Meningococcal Outer Membrane Vesicle Composition-Dependent Activation of the Innate Immune Response

2016 ◽  
Vol 84 (10) ◽  
pp. 3024-3033 ◽  
Author(s):  
Afshin Zariri ◽  
Joep Beskers ◽  
Bas van de Waterbeemd ◽  
Hendrik Jan Hamstra ◽  
Tim H. E. Bindels ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Outer Membrane ◽  
Lipid A ◽  
Membrane Vesicle ◽  
Outer Membrane Vesicles ◽  
Factor H ◽  
Innate Immune ◽  
Monocytic Cell ◽  
Monocytic Cell Line ◽  
Detergent Treatment

Meningococcal outer membrane vesicles (OMVs) have been extensively investigated and successfully implemented as vaccines. They contain pathogen-associated molecular patterns, including lipopolysaccharide (LPS), capable of triggering innate immunity. However,Neisseria meningitidiscontains an extremely potent hexa-acylated LPS, leading to adverse effects when its OMVs are applied as vaccines. To create safe OMV vaccines, detergent treatment is generally used to reduce the LPS content. While effective, this method also leads to loss of protective antigens such as lipoproteins. Alternatively, genetic modification of LPS can reduce its toxicity. In the present study, we have compared the effects of standard OMV isolation methods using detergent or EDTA with those of genetic modifications of LPS to yield a penta-acylated lipid A (lpxL1andpagL) on thein vitroinduction of innate immune responses. The use of detergent decreased both Toll-like receptor 4 (TLR4) and TLR2 activation by OMVs, while the LPS modifications reduced only TLR4 activation. Mutational removal of PorB or lipoprotein factor H binding protein (fHbp), two proteins known to trigger TLR2 signaling, had no effect, indicating that multiple TLR2 ligands are removed by detergent treatment. Detergent-treated OMVs andlpxL1OMVs showed similar reductions of cytokine profiles in the human monocytic cell line MM6 and human dendritic cells (DCs). OMVs with the alternative penta-acylated LPS structure obtained after PagL-mediated deacylation showed reduced induction of proinflammatory cytokines interleukin-6 (IL-6) and IL-1β but not of IP-10, a typical TRIF-dependent chemokine. Taken together, these data show that lipid A modification can be used to obtain OMVs with reduced activation of innate immunity, similar to what is found after detergent treatment.

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