Acidic pH-Induced Membrane Insertion of Colicin A into E. coli Natural Lipids Probed by Site-Directed Spin Labeling

Pulagam, Lakshmi Padmavathi; Steinhoff, Heinz‐Jürgen

doi:10.1016/j.jmb.2013.01.037

Cited by 11 publications

(4 citation statements)

References 66 publications

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“…The smallest pore-forming colicin is colicin N. These membrane pore-forming motifs of colicin consist of a bundle of α-helices. It was reported that during the pore formation, except colicin A, colicin E and Ia also results in an "umbrella" conformation with oligomerized dimers or higher-order assemblies, which was shown by electron paramagnetic resonance (EPR) spectra [64]. Moreover, combined with electrostatic binding to the surface and hydrophobic interaction, colicins finally form mature membrane pore.…”

Section: The Colicin Subfamilymentioning

confidence: 99%

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Structural Basis of the Pore-Forming Toxin/Membrane Interaction

Mengist

et al. 2021

Toxins

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With the rapid growth of antibiotic-resistant bacteria, it is urgent to develop alternative therapeutic strategies. Pore-forming toxins (PFTs) belong to the largest family of virulence factors of many pathogenic bacteria and constitute the most characterized classes of pore-forming proteins (PFPs). Recent studies revealed the structural basis of several PFTs, both as soluble monomers, and transmembrane oligomers. Upon interacting with host cells, the soluble monomer of bacterial PFTs assembles into transmembrane oligomeric complexes that insert into membranes and affect target cell-membrane permeability, leading to diverse cellular responses and outcomes. Herein we have reviewed the structural basis of pore formation and interaction of PFTs with the host cell membrane, which could add valuable contributions in comprehensive understanding of PFTs and searching for novel therapeutic strategies targeting PFTs and interaction with host receptors in the fight of bacterial antibiotic-resistance.

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Section: The Colicin Subfamilymentioning

confidence: 99%

“…In addition to lipid rafts, lipids themselves can directly regulate membrane pore formation. For example, E. coli colicins of β-PFT showed an anionic lipid, cardiolipin, in the bacterial inner membrane [64], promoting the umbrella pore conformation.…”

Section: Diversification Of Interaction Of Pfts With Membrane Componentsmentioning

confidence: 99%

Structural Basis of the Pore-Forming Toxin/Membrane Interaction

Mengist

et al. 2021

Toxins

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“…Subsequently, disulphide bond engineering experiments suggested an alternative ‘pen-knife model’ wherein the amphipathic helices rearrange, causing the two hydrophobic TMHs to ‘fall’ in the membrane [163]. A more recent study using site-directed spin labelling combined with EPR spectroscopy of colicin A inserted in proteoliposomes gave results that were more consistent with the umbrella model [179]. Colicin oligomerisation, following membrane insertion of monomers according to the umbrella model would be consistent with the assembly mechanism of other α-PFTs.…”

Section: Anti-bacterial Pore Forming Toxinsmentioning

confidence: 99%

Bacterial pore-forming toxins

Ulhuq

Mariano

2022

Microbiology

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Pore-forming toxins (PFTs) are widely distributed in both Gram-negative and Gram-positive bacteria. PFTs can act as virulence factors that bacteria utilise in dissemination and host colonisation or, alternatively, they can be employed to compete with rival microbes in polymicrobial niches. PFTs transition from a soluble form to become membrane-embedded by undergoing large conformational changes. Once inserted, they perforate the membrane, causing uncontrolled efflux of ions and/or nutrients and dissipating the protonmotive force (PMF). In some instances, target cells intoxicated by PFTs display additional effects as part of the cellular response to pore formation. Significant progress has been made in the mechanistic description of pore formation for the different PFTs families, but in several cases a complete understanding of pore structure remains lacking. PFTs have evolved recognition mechanisms to bind specific receptors that define their host tropism, although this can be remarkably diverse even within the same family. Here we summarise the salient features of PFTs and highlight where additional research is necessary to fully understand the mechanism of pore formation by members of this diverse group of protein toxins.

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“…Next, we mention a few more examples of spin-label EPR studies by other groups such as those of Heinz-Jürgen Steinhoff [81,288,290,[321][322][323][324][325][326][327][328][329][330][331][332][333][334][335], of Klaus Möbius [17,69,264,328,[336][337][338][339], of Thomas Prisner [242,243,[340][341][342][343][344][345][346], Olav Schiemann [33,[347][348][349][350][351][352][353][354][355][356][357][358], Gunnar Jeschke [35,…”

Section: Overview Of Studies On Nitroxide Spin-labeled Proteins and Dmentioning

confidence: 99%

Biomolecular EPR Meets NMR at High Magnetic Fields

et al. 2018

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In this review on advanced biomolecular EPR spectroscopy, which addresses both the EPR and NMR communities, considerable emphasis is put on delineating the complementarity of NMR and EPR regarding the measurement of interactions and dynamics of large molecules embedded in fluid-solution or solid-state environments. Our focus is on the characterization of protein structure, dynamics and interactions, using sophisticated EPR spectroscopy methods. New developments in pulsed microwave and sweepable cryomagnet technology as well as ultrafast electronics for signal data handling and processing have pushed the limits of EPR spectroscopy to new horizons reaching millimeter and sub-millimeter wavelengths and 15 T Zeeman fields. Expanding traditional applications to paramagnetic systems, spin-labeling of biomolecules has become a mainstream multifrequency approach in EPR spectroscopy. In the high-frequency/high-field EPR region, sub-micromolar concentrations of nitroxide spin-labeled molecules are now sufficient to characterize reaction intermediates of complex biomolecular processes. This offers promising analytical applications in biochemistry and molecular biology where sample material is often difficult to prepare in sufficient concentration for NMR characterization. For multifrequency EPR experiments on frozen solutions typical sample volumes are of the order of 250 μL (S-band), 150 μL (X-band), 10 μL (Q-band) and 1 μL (W-band). These are orders of magnitude smaller than the sample volumes required for modern liquid- or solid-state NMR spectroscopy. An important additional advantage of EPR over NMR is the ability to detect and characterize even short-lived paramagnetic reaction intermediates (down to a lifetime of a few ns). Electron–nuclear and electron–electron double-resonance techniques such as electron–nuclear double resonance (ENDOR), ELDOR-detected NMR, PELDOR (DEER) further improve the spectroscopic selectivity for the various magnetic interactions and their evolution in the frequency and time domains. PELDOR techniques applied to frozen-solution samples of doubly spin-labeled proteins allow for molecular distance measurements ranging up to about 100 Å. For disordered frozen-solution samples high-field EPR spectroscopy allows greatly improved orientational selection of the molecules within the laboratory axes reference system by means of the anisotropic electron Zeeman interaction. Single-crystal resolution is approached at the canonical g-tensor orientations—even for molecules with very small g-anisotropies. Unique structural, functional, and dynamic information about molecular systems is thus revealed that can hardly be obtained by other analytical techniques. On the other hand, the limitation to systems with unpaired electrons means that EPR is less widely used than NMR. However, this limitation also means that EPR offers greater specificity, since ordinary chemical solvents and matrices do not give rise to EPR in contrast to NMR spectra. Thus, multifrequency EPR spectroscopy plays an important role in better understanding paramagnetic species such as organic and inorganic radicals, transition metal complexes as found in many catalysts or metalloenzymes, transient species such as light-generated spin-correlated radical pairs and triplets occurring in protein complexes of photosynthetic reaction centers, electron-transfer relays, etc. Special attention is drawn to high-field EPR experiments on photosynthetic reaction centers embedded in specific sugar matrices that enable organisms to survive extreme dryness and heat stress by adopting an anhydrobiotic state. After a more general overview on methods and applications of advanced multifrequency EPR spectroscopy, a few representative examples are reviewed to some detail in two Case Studies: (I) High-field ELDOR-detected NMR (EDNMR) as a general method for electron–nuclear hyperfine spectroscopy of nitroxide radical and transition metal containing systems; (II) High-field ENDOR and EDNMR studies of the Oxygen Evolving Complex (OEC) in Photosystem II, which performs water oxidation in photosynthesis, i.e., the light-driven splitting of water into its elemental constituents, which is one of the most important chemical reactions on Earth.

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Acidic pH-Induced Membrane Insertion of Colicin A into E. coli Natural Lipids Probed by Site-Directed Spin Labeling

Cited by 11 publications

References 66 publications

Structural Basis of the Pore-Forming Toxin/Membrane Interaction

Structural Basis of the Pore-Forming Toxin/Membrane Interaction

Bacterial pore-forming toxins

Biomolecular EPR Meets NMR at High Magnetic Fields

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