scholarly journals Investigating Hydrophilic Pores in Model Lipid Bilayers Using Molecular Simulations: Correlating Bilayer Properties with Pore-Formation Thermodynamics

Langmuir ◽  
2015 ◽  
Vol 31 (24) ◽  
pp. 6615-6631 ◽  
Author(s):  
Yuan Hu ◽  
Sudipta Kumar Sinha ◽  
Sandeep Patel
Keyword(s):  
Lipid Bilayers ◽  
Pore Formation ◽  
Molecular Simulations ◽  
Formation Thermodynamics

scholarly journals Daptomycin Pore Formation and Stoichiometry Depend on Membrane Potential of Target Membrane

2018 ◽  
Vol 63 (1) ◽  
Author(s):  
Gabriela Seydlová ◽  
Albert Sokol ◽  
Petra Lišková ◽  
Ivo Konopásek ◽  
Radovan Fišer
Keyword(s):  
Membrane Potential ◽  
Lipid Bilayers ◽  
Pore Formation ◽  
Content Type ◽  
Calcium Dependent ◽  
Screening Experiment ◽  
Serious Infections ◽  
Fluorescence Methods ◽  
Initial Membrane ◽  
Target Membrane

ABSTRACT Daptomycin is a calcium-dependent lipodepsipeptide antibiotic clinically used to treat serious infections caused by Gram-positive pathogens. Its precise mode of action is somewhat controversial; the biggest issue is daptomycin pore formation, which we directly investigated here. We first performed a screening experiment using propidium iodide (PI) entry to Bacillus subtilis cells and chose the optimum and therapeutically relevant conditions (10 µg/ml daptomycin and 1.25 mM CaCl2) for the subsequent analyses. Using conductance measurements on planar lipid bilayers, we show that daptomycin forms nonuniform oligomeric pores with conductance ranging from 120 pS to 14 nS. The smallest conductance unit is probably a dimer; however, tetramers and pentamers occur in the membrane most frequently. Moreover, daptomycin pore-forming activity is exponentially dependent on the applied membrane voltage. We further analyzed the membrane-permeabilizing activity in B. subtilis cells using fluorescence methods [PI and DiSC3(5)]. Daptomycin most rapidly permeabilizes cells with high initial membrane potential and dissipates it within a few minutes. Low initial membrane potential hinders daptomycin pore formation.

155. Atomistic investigations of spontaneous unstable pore formation in DMPC lipid bilayers due to the presence of Me2SO

Cryobiology ◽  
2007 ◽  
Vol 55 (3) ◽  
pp. 375-376
Author(s):  
Dinesh Pinisetty ◽  
Dorel Moldovan ◽  
Ram Devireddy
Keyword(s):  
Lipid Bilayers ◽  
Pore Formation

scholarly journals Engineered covalent leucotoxin heterodimers form functional pores: insights into S–F interactions

2006 ◽  
Vol 396 (2) ◽  
pp. 381-389 ◽  
Author(s):  
Olivier Joubert ◽  
Gabriella Viero ◽  
Daniel Keller ◽  
Eric Martinez ◽  
Didier A. Colin ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Pore Formation ◽  
Polymorphonuclear Neutrophils ◽  
Target Cells ◽  
Single Family ◽  
Wild Type ◽  
Subunit Interactions ◽  
Human Red Blood Cells ◽  
Large Unilamellar Vesicles ◽  
New Strategy

The staphylococcal α-toxin and bipartite leucotoxins belong to a single family of pore-forming toxins that are rich in β-strands, although the stoichiometry and electrophysiological characteristics of their pores are different. The different known structures show a common β-sandwich domain that plays a key role in subunit–subunit interactions, which could be targeted to inhibit oligomerization of these toxins. We used several cysteine mutants of both HlgA (γ-haemolysin A) and HlgB (γ-haemolysin B) to challenge 20 heterodimers linked by disulphide bridges. A new strategy was developed in order to obtain a good yield for S-S bond formation and dimer stabilization. Functions of the pores formed by 14 purified dimers were investigated on model membranes, i.e. planar lipid bilayers and large unilamellar vesicles, and on target cells, i.e. rabbit and human red blood cells and polymorphonuclear neutrophils. We observed that dimers HlgA T28C–HlgB N156C and HlgA T21C–HlgB T157C form pores with similar characteristics as the wild-type toxin, thus suggesting that the mutated residues are facing one another, allowing pore formation. Our results also confirm the octameric stoichiometry of the leucotoxin pores, as well as the parity of the two monomers in the pore. Correctly assembled heterodimers thus constitute the minimal functional unit of leucotoxins. We propose amino acids involved in interactions at one of the two interfaces for an assembled leucotoxin.

scholarly journals Probing the Ripple Phase of Lipid Bilayers using Molecular Simulations

2016 ◽  
Vol 110 (3) ◽  
pp. 86a ◽  
Author(s):  
Pouyan Khakbaz ◽  
Jeffery Klauda
Keyword(s):  
Lipid Bilayers ◽  
Molecular Simulations ◽  
Ripple Phase

Interaction of reducible polypeptide gene delivery vectors with supported lipid bilayers: pore formation and structure–function relationships

Soft Matter ◽  
2010 ◽  
Vol 6 (11) ◽  
pp. 2517 ◽  
Author(s):  
Mahmoud Soliman ◽  
Rujikan Nasanit ◽  
Stephanie Allen ◽  
Martyn C. Davies ◽  
Simon S. Briggs ◽  
...  
Keyword(s):  
Gene Delivery ◽  
Structure Function ◽  
Lipid Bilayers ◽  
Pore Formation ◽  
Supported Lipid Bilayers ◽  
Gene Delivery Vectors

scholarly journals Pore formation by pho-controlled outer-membrane proteins of various Enterobacteriaceae in lipid bilayers

1988 ◽  
Vol 174 (1) ◽  
pp. 199-205 ◽  
Author(s):  
Katharina BAUER ◽  
Angela SCHMID ◽  
Winfried BOOS ◽  
Roland BENZ ◽  
Jan TOMMASSEN
Keyword(s):  
Membrane Proteins ◽  
Outer Membrane ◽  
Lipid Bilayers ◽  
Pore Formation ◽  
Outer Membrane Proteins

scholarly journals Bax-type Apoptotic Proteins Porate Pure Lipid Bilayers through a Mechanism Sensitive to Intrinsic Monolayer Curvature

2002 ◽  
Vol 277 (51) ◽  
pp. 49360-49365 ◽  
Author(s):  
Gorka Basañez ◽  
Juanita C. Sharpe ◽  
Jennifer Galanis ◽  
Teresa B. Brandt ◽  
J. Marie Hardwick ◽  
...  
Keyword(s):  
Lipid Bilayers ◽  
Mitochondrial Membrane ◽  
Pore Formation ◽  
Membrane Binding ◽  
Membrane Permeabilization ◽  
Outer Mitochondrial Membrane ◽  
Intrinsic Curvature ◽  
Differential Effects ◽  
Cleavage Fragment ◽  
Induced Changes

During apoptosis, Bax-type proteins permeabilize the outer mitochondrial membrane to release intermembrane apoptogenic factors into the cytosol via a poorly understood mechanism. We have proposed that Bax and ΔN76Bcl-xL(the Bax-like cleavage fragment of Bcl-xL) function by forming pores that are at least partially composed of lipids (lipidic pore formation). Since the membrane monolayer must bend during lipidic pore formation, we here explore the effect of intrinsic membrane monolayer curvature on pore formation. Nonlamellar lipids with positive intrinsic curvature such as lysophospholipids promoted membrane permeabilization, whereas nonlamellar lipids with negative intrinsic curvature such as diacylglycerol and phosphatidylethanolamine inhibited membrane permeabilization. The differential effects of nonlamellar lipids on membrane permeabilization were not correlated with lipid-induced changes in membrane binding or insertion of Bax or ΔN76Bcl-xL. Altogether, these results are consistent with a model whereby Bax-type proteins change the bending propensity of the membrane to form pores comprised at least in part of lipids in a structure of net positive monolayer curvature.

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