scholarly journals Unraveling the host-selective toxic interaction of cassiicolin with lipid membranes and its cytotoxicity

2021 ◽  
Author(s):  
Kien Xuan Ngo ◽  
Nguyen Bao Quoc ◽  
Phuong Doan N. Nguyen ◽  
Hirotoshi Furusho ◽  
Makoto Miyata ◽  
...  
Keyword(s):  
Lipid Membranes ◽  
High Speed ◽  
Membrane Lipids ◽  
Membrane Damage ◽  
Binding Activity ◽  
Force Microscopy ◽  
Plant Lipids ◽  
Host Selectivity ◽  
Leaf Tissues ◽  
Cas A

Corynespora cassiicola is the pathogen that causes Corynespora leaf fall (CLF) disease. Cassiicolin (Cas), a toxin produced by C. cassiicola, is responsible for CLF disease in rubber trees (Hevea brasiliensis). Currently, the molecular mechanism of the cytotoxicity of Cas and its host selectivity have not been fully elucidated. To gain insight into these issues, we analyzed the binding of Cas1 and Cas2 to membranes consisting of different plant lipids and their membrane-disruption activities. Our real-time observations with high-speed atomic force microscopy (HS-AFM) and confocal microscopy reveal that the binding and disruption activities of Cas1 and Cas2 are strongly dependent on the types of membrane lipids. The mixtures of DPPC with DPPA, MGDG, DGDG, and stigmasterol are more susceptible to membrane damage caused by Cas1 and Cas2 than DPPC alone or its mixtures with sitosterol, DGTS-d9, and DGTS. This difference derives from the stronger binding of the toxins to membranes with the former lipid composition. Cytotoxicity tests on rubber leaves of RRIV 1, RRIV 4, and PB 255 clones suggest that the toxins cause necrosis of rubber leaves, except for the strong resistance of PB 255 against Cas2. Cryo-SEM analyses of necrotic leaf tissues exposed to Cas1 confirm that cytoplasmic membranes are vulnerable to the toxin. Thus, the host selectivity of Cas toxin in CLF disease is attained by the lipid-dependent binding activity of Cas to the membrane, and the cytotoxicity of Cas arises from its ability to disrupt membranes.

scholarly journals Studying biological membranes with extended range high-speed atomic force microscopy

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Adrian P. Nievergelt ◽  
Blake W. Erickson ◽  
Nahid Hosseini ◽  
Jonathan D. Adams ◽  
Georg E. Fantner
Keyword(s):  
Atomic Force Microscopy ◽  
Lipid Membranes ◽  
High Speed ◽  
Open Loop ◽  
Peak Force ◽  
High Speed Imaging ◽  
Biomolecular Systems ◽  
Biologically Relevant ◽  
Force Microscopy ◽  
Atomic Force

Abstract High—speed atomic force microscopy has proven to be a valuable tool for the study of biomolecular systems at the nanoscale. Expanding its application to larger biological specimens such as membranes or cells has, however, proven difficult, often requiring fundamental changes in the AFM instrument. Here we show a way to utilize conventional AFM instrumentation with minor alterations to perform high-speed AFM imaging with a large scan range. Using a two—actuator design with adapted control systems, a 130 × 130 × 5 μm scanner with nearly 100 kHz open—loop small-signal Z—bandwidth is implemented. This allows for high-speed imaging of biologically relevant samples as well as high-speed measurements of nanomechanical surface properties. We demonstrate the system performance by real-time imaging of the effect of charged polymer nanoparticles on the integrity of lipid membranes at high imaging speeds and peak force tapping measurements at 32 kHz peak force rate.

scholarly journals Real-time dynamics of carbon nanotube porins in supported lipid membranes visualized by high-speed atomic force microscopy

2017 ◽  
Vol 372 (1726) ◽  
pp. 20160226 ◽  
Author(s):  
Yuliang Zhang ◽  
Ramya H. Tunuguntla ◽  
Pyung-On Choi ◽  
Aleksandr Noy
Keyword(s):  
Atomic Force Microscopy ◽  
Carbon Nanotube ◽  
Real Time ◽  
Diffusion Coefficients ◽  
Lipid Membranes ◽  
High Speed ◽  
Time Dynamics ◽  
Force Microscopy ◽  
Atomic Force ◽  
Supported Lipid Membranes

In-plane mobility of proteins in lipid membranes is one of the fundamental mechanisms supporting biological functionality. Here we use high-speed atomic force microscopy (HS-AFM) to show that a novel type of biomimetic channel—carbon nanotube porins (CNTPs)—is also laterally mobile in supported lipid membranes, mimicking biological protein behaviour. HS-AFM can capture real-time dynamics of CNTP motion in the supported lipid bilayer membrane, build long-term trajectories of the CNTP motion and determine the diffusion coefficients associated with this motion. Our analysis shows that diffusion coefficients of CNTPs fall into the same range as those of proteins in supported lipid membranes. CNTPs in HS-AFM experiments often exhibit ‘directed’ diffusion behaviour, which is common for proteins in live cell membranes. This article is part of the themed issue ‘Membrane pores: from structure and assembly, to medicine and technology’.

scholarly journals Interactions of Linear Analogues of Battacin with Negatively Charged Lipid Membranes

Membranes ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 192
Author(s):  
Kinga Burdach ◽  
Dagmara Tymecka ◽  
Aneta Urban ◽  
Robert Lasek ◽  
Dariusz Bartosik ◽  
...  
Keyword(s):  
Lipid Membranes ◽  
Liquid Crystalline ◽  
Lipid Membrane ◽  
Attenuated Total Reflection ◽  
Gram Positive ◽  
Insertion Depth ◽  
Force Microscopy ◽  
Acyl Chains ◽  
Hydrophobic Portion ◽  
Membrane Fluidization

The increasing resistance of bacteria to available antibiotics has stimulated the search for new antimicrobial compounds with less specific mechanisms of action. These include the ability to disrupt the structure of the cell membrane, which in turn leads to its damage. In this context, amphiphilic lipopeptides belong to the class of the compounds which may fulfill this requirement. In this paper, we describe two linear analogues of battacin with modified acyl chains to tune the balance between the hydrophilic and hydrophobic portion of lipopeptides. We demonstrate that both compounds display antimicrobial activity with the lowest values of minimum inhibitory concentrations found for Gram-positive pathogens. Therefore, their mechanism of action was evaluated on a molecular level using model lipid films mimicking the membrane of Gram-positive bacteria. The surface pressure measurements revealed that both lipopeptides show ability to bind and incorporate into the lipid monolayers, resulting in decreased ordering of lipids and membrane fluidization. Atomic force microscopy (AFM) imaging demonstrated that the exposure of the model bilayers to lipopeptides leads to a transition from the ordered gel phase to disordered liquid crystalline phase. This observation was confirmed by attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) results, which revealed that lipopeptide action causes a substantial increase in the average tilt angle of lipid acyl chains with respect to the surface normal to compensate for lipopeptide insertion into the membrane. Moreover, the peptide moieties in both molecules do not adopt any well-defined secondary structure upon binding with the lipid membrane. It was also observed that a small difference in the structure of a lipophilic chain, altering the balance between hydrophobic and hydrophilic portion of the molecules, results in different insertion depth of the active compounds.

scholarly journals Histone variant H2A.B-H2B dimers are spontaneously exchanged with canonical H2A-H2B in the nucleosome

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Rina Hirano ◽  
Yasuhiro Arimura ◽  
Tomoya Kujirai ◽  
Mikihiro Shibata ◽  
Aya Okuda ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Dna Repair ◽  
High Speed ◽  
Histone Chaperones ◽  
Histone H2a ◽  
Force Microscopy ◽  
Atomic Force ◽  
Open Conformation ◽  
Replication Sites ◽  
Histone Exchange

AbstractH2A.B is an evolutionarily distant histone H2A variant that accumulates on DNA repair sites, DNA replication sites, and actively transcribing regions in genomes. In cells, H2A.B exchanges rapidly in chromatin, but the mechanism has remained enigmatic. In the present study, we found that the H2A.B-H2B dimer incorporated within the nucleosome exchanges with the canonical H2A-H2B dimer without assistance from additional factors, such as histone chaperones and nucleosome remodelers. High-speed atomic force microscopy revealed that the H2A.B nucleosome, but not the canonical H2A nucleosome, transiently forms an intermediate “open conformation”, in which two H2A.B-H2B dimers may be detached from the H3-H4 tetramer and bind to the DNA regions near the entry/exit sites. Mutational analyses revealed that the H2A.B C-terminal region is responsible for the adoption of the open conformation and the H2A.B-H2B exchange in the nucleosome. These findings provide mechanistic insights into the histone exchange of the H2A.B nucleosome.

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