Quartz Crystal Microbalances as Tools for Probing Protein–Membrane Interactions

Nielsen, Søren Achim; Otzen, Daniel E.

doi:10.1007/978-1-4939-9512-7_2

Cited by 12 publications

(9 citation statements)

References 60 publications

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“…After SLB formation at 37 °C, full surface coverage and absence of noncollapsed SUVs were confirmed (Figure S2) in line with previous results ,, and studies where neutron reflectometry was used to demonstrate defect-free bilayers. , The addition of different PS NPs to such preformed lipid bilayers (performed at 25 °C) induced an increase in mass of the resonator detectable by a decrease in frequency (Δ F ) and an increase in dissipation (Δ D ) (Figures A,B and ). This indicates that all studied PS NPs are able to reach the bilayer surface and interact with the SLB, with the positively charged PS-NH 2 showing the largest changes (by an order of magnitude) both in frequency and dissipation (Figure ).…”

Section: Resultssupporting

confidence: 88%

“…33−35 Of note, this composition is similar to the membrane of the Artemia franciscana brine shrimp eyes, 36−38 a species widely used in toxicology and particularly to assess the toxicity of plastic NPs. 15,39,74−76 After SLB formation at 37 °C, full surface coverage and absence of noncollapsed SUVs were confirmed (Figure S2) in line with previous results 57,77,78 and studies where neutron reflectometry was used to demonstrate defect-free bilayers. 55,79 The addition of different PS NPs to such preformed lipid bilayers (performed at 25 °C) induced an increase in mass of the resonator detectable by a decrease in frequency (ΔF) and an increase in dissipation (ΔD) (Figures 2A,B and 3).…”

Section: ■ Introductionmentioning

confidence: 99%

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Surface-Functionalized Polystyrene Nanoparticles Alter the Transmembrane Potential via Ion-Selective Pores Maintaining Global Bilayer Integrity

et al. 2022

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Although nanoplastics have well-known toxic effects toward the environment and living organisms, their molecular toxicity mechanisms, including the nature of nanoparticle–cell membrane interactions, are still under investigation. Here, we employ dynamic light scattering, quartz crystal microbalance with dissipation monitoring, and electrophysiology to investigate the interaction between polystyrene nanoparticles (PS NPs) and phospholipid membranes. Our results show that PS NPs adsorb onto lipid bilayers creating soft inhomogeneous films that include disordered defects. PS NPs form an integral part of the generated channels so that the surface functionalization and charge of the NP determine the pore conductive properties. The large difference in size between the NP diameter and the lipid bilayer thickness (∼60 vs ∼5 nm) suggests a particular and complex lipid–NP assembly that is able to maintain overall membrane integrity. In view of this, we suggest that NP-induced toxicity in cells could operate in more subtle ways than membrane disintegration, such as inducing lipid reorganization and transmembrane ionic fluxes that disrupt the membrane potential.

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Section: Resultssupporting

confidence: 88%

Section: ■ Introductionmentioning

confidence: 99%

Surface-Functionalized Polystyrene Nanoparticles Alter the Transmembrane Potential via Ion-Selective Pores Maintaining Global Bilayer Integrity

et al. 2022

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“…To exclude that binding was affected by the non-physiological positive curvature of the liposomes, a complementary experiment was carried out using planar supported lipid bilayers (SLBs) deposited on a quartz crystal microbalance (QCM) chip [31]. Liposomes were non-covalently adsorbed on the quartz chip surface and fused to form continuous SLBs (Figure 10A and B).…”

Section: Unsaturated Fatty Acids Facilitate Seca Binding To the Lipid Bilayermentioning

confidence: 99%

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

et al. 2021

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The translocon SecYEG and the associated ATPase SecA form the primary protein secretion system in the cytoplasmic membrane of bacteria. The secretion is essentially dependent on the surrounding lipids, but the mechanistic understanding of their role in SecA : SecYEG activity is sparse. Here, we reveal that the unsaturated fatty acids (UFAs) of the membrane phospholipids, including tetraoleoyl-cardiolipin, stimulate SecA : SecYEGmediated protein translocation up to ten-fold. Biophysical analysis and molecular dynamics simulations show that UFAs increase the area per lipid and cause loose packing of lipid head groups, 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 up to fivefold at elevated ionic strength. Tight SecA : lipid interactions convert into the augmented translocation. Our results identify the fatty acid structure as a notable factor in SecA : SecYEG activity, which may be crucial for protein secretion in bacteria, which actively change their membrane composition in response to their habitat.

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“…To exclude that binding was affected by the non-physiological positive curvature of the liposomes, a complementary experiment was carried out using planar supported lipid bilayers (SLBs) deposited on a quartz crystal microbalance (QCM) chip [27]. Liposomes were noncovalently adsorbed on the quartz chip surface and fused to form continuous SLBs (Suppl.…”

Section: Unsaturated Fatty Acids Facilitate Seca Binding To the Lipid Bilayermentioning

confidence: 99%

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

Kamel

Löwe

Schott‐Verdugo

et al. 2021

Preprint

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The 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.

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Quartz Crystal Microbalances as Tools for Probing Protein–Membrane Interactions

Cited by 12 publications

References 60 publications

Surface-Functionalized Polystyrene Nanoparticles Alter the Transmembrane Potential via Ion-Selective Pores Maintaining Global Bilayer Integrity

Surface-Functionalized Polystyrene Nanoparticles Alter the Transmembrane Potential via Ion-Selective Pores Maintaining Global Bilayer Integrity

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

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

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