scholarly journals Biophysical Reviews’ “Meet the Councilor Series”—a profile of Peter Pohl

2021 ◽  
Author(s):  
Peter Pohl
Keyword(s):  
Molecular Mechanisms ◽  
Lipid Membrane ◽  
Protein Translocation ◽  
Membrane Surface ◽  
Academic Disciplines ◽  
Johannes Kepler ◽  
Humboldt University ◽  
Proton Migration ◽  
Physics Department ◽  
Postdoctoral Researchers

AbstractIt is my pleasure to write a few words to introduce myself to the readers of Biophysical Reviews as part of the “Meet the Councilor Series.” Currently, I am serving the second period as IUPAB councilor after having been elected first in 2017. Initially, I studied Biophysics in Moscow (Russia) and later Medicine in Halle (Germany). My scientific carrier took me from the Medical School of the Martin Luther University of Halle-Wittenberg, via the Leibniz Institute for Molecular Pharmacology (Berlin) and the Institute for Biology at the Humboldt University (Berlin) to the Physics Department of the Johannes Kepler University in Linz (Austria). My key research interests lie in the molecular mechanisms of transport phenomena occurring at the lipid membrane, including (i) spontaneous and facilitated transport of water and other small molecules across membranes in reconstituted systems, (ii) proton migration along the membrane surface, (iii) protein translocation, and (iv) bilayer mechanics. Training of undergraduate, graduate, and postdoctoral researchers from diverse academic disciplines has been—and shall remain—a consistent part of my work.

Maintaining the permeability barrier during protein trafficking at the endoplasmic reticulum membrane

2003 ◽  
Vol 31 (6) ◽  
pp. 1227-1231 ◽  
Author(s):  
A.E. Johnson
Keyword(s):  
Endoplasmic Reticulum ◽  
Small Molecule ◽  
Protein Trafficking ◽  
Molecular Mechanisms ◽  
Protein Translocation ◽  
Cellular Membrane ◽  
Permeability Barrier ◽  
Endoplasmic Reticulum Membrane ◽  
Ion Diffusion

Many proteins are translocated across or integrated into a cellular membrane without disrupting its integrity, although it is difficult to imagine how such macromolecular transmembrane movement can occur without simultaneously allowing significant small-molecule and ion diffusion across the bilayer. Recent studies have identified some molecular mechanisms that are involved in maintaining the permeability barrier of the endoplasmic reticulum membrane during co-translational protein translocation and integration. These mechanisms are both simple and direct in concept, but are operationally complex and require the co-ordinated and regulated interaction of several multicomponent complexes.

scholarly journals Membrane phospholipid composition affects function of potassium channels from rabbit colon epithelium

1999 ◽  
Vol 277 (1) ◽  
pp. C83-C90 ◽  
Author(s):  
Klaus Turnheim ◽  
Johannes Gruber ◽  
Christoph Wachter ◽  
Valentina Ruiz-Gutiérrez
Keyword(s):  
Surface Potential ◽  
Lipid Membrane ◽  
Single Channel ◽  
Membrane Surface ◽  
Phospholipid Composition ◽  
Distal Colon ◽  
Membrane Phospholipids ◽  
Channel Conductance ◽  
Planar Bilayers ◽  
Conduction Pathway

We tested the effects of membrane phospholipids on the function of high-conductance, Ca2+-activated K+ channels from the basolateral cell membrane of rabbit distal colon epithelium by reconstituting these channels into planar bilayers consisting of different 1:1 mixtures of phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylserine (PS), and phosphatidylinositol (PI). At low ambient K+ concentrations single-channel conductance is higher in PE/PS and PE/PI bilayers than in PE/PC bilayers. At high K+concentrations this difference in channel conductance is abolished. Introducing the negatively charged SDS into PE/PC bilayers increases channel conductance, whereas the positively charged dodecyltrimethylammonium has the opposite effect. All these findings are consistent with modulation of channel current by the charge of the lipid membrane surrounding the channel. But the K+ that permeates the channel senses only a small fraction of the full membrane surface potential of the charged phospholipid bilayers, equivalent to separation of the conduction pathway from the charged phospholipid head groups by 20Å. This distance appears to insulate the channel entrance from the bilayer surface potential, suggesting large dimensions of the channel-forming protein. In addition, in PE/PC and PE/PI bilayers, but not in PE/PS bilayers, the open-state probability of the channel decreases with time (“channel rundown”), indicating that phospholipid properties other than surface charge are required to maintain channel fluctuations.

scholarly journals Membrane Deformation of Endothelial Surface Layer Interspersed with Syndecan-4: A Molecular Dynamics Study

2019 ◽  
Vol 48 (1) ◽  
pp. 357-366 ◽  
Author(s):  
Xi Zhuo Jiang ◽  
Liwei Guo ◽  
Kai H. Luo ◽  
Yiannis Ventikos
Keyword(s):  
Molecular Dynamics ◽  
Lipid Membrane ◽  
Environmental Changes ◽  
Core Protein ◽  
Membrane Surface ◽  
Circulatory System ◽  
Endothelial Glycocalyx ◽  
Force Transmission ◽  
Membrane Deformation ◽  
The Core

Abstract The lipid membrane of endothelial cells plays a pivotal role in maintaining normal circulatory system functions. To investigate the response of the endothelial cell membrane to changes in vascular conditions, an atomistic model of the lipid membrane interspersed with Syndecan-4 core protein was established based on experimental observations and a series of molecular dynamics simulations were undertaken. The results show that flow results in continuous deformation of the lipid membrane, and the degree of membrane deformation is not in monotonic relationship with the environmental changes (either the changes in blood velocity or the alteration of the core protein configuration). An explanation for such non-monotonic relationship is provided, which agrees with previous experimental results. The elevation of the lipid membrane surface around the core protein of the endothelial glycocalyx was also observed, which can be mainly attributed to the Coulombic interactions between the biomolecules therein. The present study demonstrates that the blood flow can deform the lipid membrane directly via the interactions between water molecules and lipid membrane atoms thereby affecting mechanosensing; it also presents an additional force transmission pathway from the flow to the lipid membrane via the glycocalyx core protein, which complements previous mechanotransduction hypothesis.

scholarly journals The molecular mechanisms of listeriolysin O-induced lipid membrane damage

2021 ◽  
pp. 183604
Author(s):  
Nejc Petrišič ◽  
Mirijam Kozorog ◽  
Saša Aden ◽  
Marjetka Podobnik ◽  
Gregor Anderluh
Keyword(s):  
Molecular Mechanisms ◽  
Lipid Membrane ◽  
Membrane Damage ◽  
Listeriolysin O

scholarly journals Escherichia coli response to subinhibitory concentration of Colistin: Insights from study of membrane dynamics and morphology.

2022 ◽  
Author(s):  
Ilanila Ilangumaran Ponmalar ◽  
Jitendriya Swain ◽  
Jaydeep Kumar Basu
Keyword(s):  
Bacterial Infections ◽  
Molecular Mechanisms ◽  
Lipid Membrane ◽  
Membrane Dynamics ◽  
Correlation Spectroscopy ◽  
Membrane Properties ◽  
Bacterial Response ◽  
Lipid Dynamics ◽  
The Impact ◽  
Altered Lipid

Prevalence of wide spread bacterial infections bring forth a critical need in understanding the molecular mechanisms of the antibiotics as well as the bacterial response to those antibiotics. Improper usage of antibiotics, which can be in sub-lethal concentrations is one among the multiple reasons for acquiring antibiotic resistance which makes it vital to understand the bacterial response towards sub-lethal concentrations of antibiotics. In this work, we have used colistin, a well-known membrane active antibiotic used to treat severe bacterial infections and explored the impact of its subminimum inhibitory concentration (MIC) on the lipid membrane dynamics and morphological changes of E. coli. Upon investigation of live cell membrane properties such as lipid dynamics using fluorescence correlation spectroscopy, we observed that colistin disrupts the lipid membrane at sub-MIC by altering the lipid diffusivity. Interestingly, filamentationlike cell elongation was observed upon colistin treatment which led to further exploration of surface morphology with the help of atomic force spectroscopy. The changes in the surface roughness upon colistin treatment provides additional insight on the colistin-membrane interaction corroborating with the altered lipid diffusion. Although altered lipid dynamics could be attributed to an outcome of lipid rearrangement due to direct disruption by antibiotic molecules on the membrane or an indirect consequence of disruptions in lipid biosynthetic pathways, we were able to ascertain that altered bacterial membrane dynamics is due to direct disruptions. Our results provide a broad overview on the consequence of the cyclic polypeptide, colistin on membrane specific lipid dynamics and morphology of a live Gram-negative bacterial cell.

scholarly journals Unsaturated fatty acids augment protein transport via the SecA:SecYEG translocon

2021 ◽  
Author(s):  
Michael Kamel ◽  
Maryna Löwe ◽  
Stephan Schott-Verdugo ◽  
Holger Gohlke ◽  
Alexej Kedrov
Keyword(s):  
Fatty Acids ◽  
Protein Transport ◽  
Unsaturated Fatty Acids ◽  
Lipid Membrane ◽  
Cell Envelope ◽  
Membrane Surface ◽  
Bacterial Cells ◽  
Hydrophobic Core ◽  
Membrane Composition ◽  
Dynamics Simulations

AbstractThe translocon SecYEG forms the primary protein-conducting channel in the cytoplasmic membrane of bacteria, and the associated ATPase SecA provides the energy for the transport of secretory and cell envelope protein precursors. The translocation requires negative charge at the lipid membrane surface, but its dependence on the properties of the membrane hydrophobic core is not known. Here, we demonstrate that SecA:SecYEG-mediated protein transport is immensely stimulated by unsaturated fatty acids (UFAs). Furthermore, UFA-rich tetraoleoyl-cardiolipin, but not bis(palmitoyloleoyl)-cardiolipin, facilitate the translocation via the monomeric translocon. Biophysical analysis and molecular dynamics simulations show that UFAs determine the loosely packed membrane interface, where the N-terminal amphipathic helix of SecA docks. While UFAs do not affect the translocon folding, they promote SecA binding to the membrane, and the effect is enhanced manifold at elevated ionic strength. Tight SecA:lipid interactions convert into the augmented translocation. As bacterial cells actively change their membrane composition in response to their habitat, the modulation of SecA:SecYEG activity via the fatty acids may be crucial for protein secretion over a broad range of environmental conditions.

scholarly journals Physical mechanisms of amyloid nucleation on fluid membranes

2020 ◽  
Vol 117 (52) ◽  
pp. 33090-33098
Author(s):  
Johannes Krausser ◽  
Tuomas P. J. Knowles ◽  
Anđela Šarić
Keyword(s):  
Lipid Membranes ◽  
Molecular Mechanisms ◽  
Amyloid Fibrils ◽  
Lipid Membrane ◽  
Coarse Grained ◽  
Coarse Grained Model ◽  
Physical Mechanisms ◽  
Fluid Membranes ◽  
Protein Membrane ◽  
Protein Rich

Biological membranes can dramatically accelerate the aggregation of normally soluble protein molecules into amyloid fibrils and alter the fibril morphologies, yet the molecular mechanisms through which this accelerated nucleation takes place are not yet understood. Here, we develop a coarse-grained model to systematically explore the effect that the structural properties of the lipid membrane and the nature of protein–membrane interactions have on the nucleation rates of amyloid fibrils. We identify two physically distinct nucleation pathways—protein-rich and lipid-rich—and quantify how the membrane fluidity and protein–membrane affinity control the relative importance of those molecular pathways. We find that the membrane’s susceptibility to reshaping and being incorporated into the fibrillar aggregates is a key determinant of its ability to promote protein aggregation. We then characterize the rates and the free-energy profile associated with this heterogeneous nucleation process, in which the surface itself participates in the aggregate structure. Finally, we compare quantitatively our data to experiments on membrane-catalyzed amyloid aggregation of α-synuclein, a protein implicated in Parkinson’s disease that predominately nucleates on membranes. More generally, our results provide a framework for understanding macromolecular aggregation on lipid membranes in a broad biological and biotechnological context.

scholarly journals Modelling of the Citrus CCD4 Family Members: In Silico Analysis of Membrane Binding and Substrate Preference

2021 ◽  
Vol 22 (24) ◽  
pp. 13616
Author(s):  
Jorge Cantero ◽  
Fabio Polticelli ◽  
Margot Paulino
Keyword(s):  
Lipid Membrane ◽  
Membrane Surface ◽  
Family Members ◽  
In Silico Analysis ◽  
Depth Of Penetration ◽  
Ligand Interaction ◽  
Catalytic Center ◽  
Hydrophobic Residues ◽  
Protein Ligand Interaction ◽  
Silico Analysis

Coloring is one of the most important characteristics in commercial flowers and fruits, generally due to the accumulation of carotenoid pigments. Enzymes of the CCD4 family in citrus intervene in the generation of β-citraurin, an apocarotenoid responsible for the reddish-orange color of mandarins. Citrus CCD4s enzymes could be capable of interacting with the thylakoid membrane inside chloroplasts. However, to date, this interaction has not been studied in detail. In this work, we present three new complete models of the CCD4 family members (CCD4a, CCD4b, and CCD4c), modeled with a lipid membrane. To identify the preference for substrates, typical carotenoids were inserted in the active site of the receptors and the protein–ligand interaction energy was evaluated. The results show a clear preference of CCD4s for xanthophylls over aliphatic carotenes. Our findings indicate the ability to penetrate the membrane and maintain a stable interaction through the N-terminal α-helical domain, spanning a contact surface of 2250 to 3250 Å2. The orientation and depth of penetration at the membrane surface suggest that CCD4s have the ability to extract carotenoids directly from the membrane through a tunnel consisting mainly of hydrophobic residues that extends up to the catalytic center of the enzyme.

Sign in / Sign up

Export Citation Format

Share Document