1
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Di Bartolo AL, Caparotta M, Masone D. Intrinsic Disorder in α-Synuclein Regulates the Exocytotic Fusion Pore Transition. ACS Chem Neurosci 2023. [PMID: 37192400 DOI: 10.1021/acschemneuro.3c00040] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2023] Open
Abstract
Today, it is widely accepted that intrinsic disorder is strongly related to the cell cycle, during mitosis, differentiation, and apoptosis. Of particular interest are hybrid proteins possessing both structured and unstructured domains that are critical in human health and disease, such as α-synuclein. In this work, we describe how α-synuclein interacts with the nascent fusion pore as it evolves toward expansion. We unveil the key role played by its intrinsically disordered region as a thermodynamic regulator of the nucleation-expansion energy barrier. By analyzing a truncated variant of α-synuclein that lacks the disordered region, we find that the landscape of protein interactions with PIP2 and POPS lipids is highly altered, ultimately increasing the energy cost for the fusion pore to transit from nucleation to expansion. We conclude that the intrinsically disordered region in full-length α-synuclein recognizes and allocates pivotal protein:lipid interactions during membrane remodeling in the first stages of the fusion pore.
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Affiliation(s)
- Ary Lautaro Di Bartolo
- Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina
| | - Marcelo Caparotta
- Quantum Theory Project, Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States
| | - Diego Masone
- Instituto de Histología y Embriología de Mendoza (IHEM) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina
- Facultad de Ingeniería, Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina
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2
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Di Bartolo AL, Tomes CN, Mayorga LS, Masone D. Enhanced Expansion and Reduced Kiss-and-Run Events in Fusion Pores Steered by Synaptotagmin-1 C2B Domains. J Chem Theory Comput 2022; 18:4544-4554. [PMID: 35759758 DOI: 10.1021/acs.jctc.2c00424] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The fusion pore controls the release of exocytotic vesicle contents through a precise orchestration of lipids from the fusing membranes and proteins. There is a major lipid reorganization during the different stages in life of the fusion pore (membrane fusion, nucleation, and expansion) that can be scrutinized thermodynamically. In this work, using umbrella sampling simulations we describe the expansion of the fusion pore. We have calculated free energy profiles to drive a nascent, just nucleated, fusion pore to its expanded configuration. We have quantified the effects on the free energy of one and two Synaptotagmin-1 C2B domains in the cytosolic space. We show that C2B domains cumulatively reduce the cost for expansion, favoring the system to evolve toward full fusion. Finally, by conducting thousands of unbiased molecular dynamics simulations, we show that C2B domains significantly decrease the probability of kiss-and-run events.
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Affiliation(s)
- Ary Lautaro Di Bartolo
- Instituto de Histología y Embriología de Mendoza (IHEM), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina.,Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina
| | - Claudia N Tomes
- Instituto de Histología y Embriología de Mendoza (IHEM), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina.,Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina
| | - Luis S Mayorga
- Instituto de Histología y Embriología de Mendoza (IHEM), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina.,Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina
| | - Diego Masone
- Instituto de Histología y Embriología de Mendoza (IHEM), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina.,Facultad de Ingeniería, Universidad Nacional de Cuyo (UNCuyo), 5500 Mendoza, Argentina
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3
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Riedlová K, Dolejšová T, Fišer R, Cwiklik L. H1 helix of colicin U causes phospholipid membrane permeation. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183866. [PMID: 35007517 DOI: 10.1016/j.bbamem.2022.183866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 12/29/2021] [Accepted: 01/03/2022] [Indexed: 06/14/2023]
Abstract
In light of an increasing number of antibiotic-resistant bacterial strains, it is essential to understand an action imposed by various antimicrobial agents on bacteria at the molecular level. One of the leading mechanisms of killing bacteria is related to the alteration of their plasmatic membrane. We study bio-inspired peptides originating from natural antimicrobial proteins colicins, which can disrupt membranes of bacterial cells. Namely, we focus on the α-helix H1 of colicin U, produced by bacterium Shigella boydii, and compare it with analogous peptides derived from two different colicins. To address the behavior of the peptides in biological membranes, we employ a combination of molecular simulations and experiments. We use molecular dynamics simulations to show that all three peptides are stable in model zwitterionic and negatively charged phospholipid membranes. At the molecular level, their embedment leads to the formation of membrane defects, membrane permeation for water, and, for negatively charged lipids, membrane poration. These effects are caused by the presence of polar moieties in the considered peptides. Importantly, simulations demonstrate that even monomeric H1 peptides can form toroidal pores. At the macroscopic level, we employ experimental co-sedimentation and fluorescence leakage assays. We show that the H1 peptide of colicin U incorporates into phospholipid vesicles and disrupts their membranes, causing leakage, in agreement with the molecular simulations. These insights obtained for model systems seem important for understanding the mechanisms of antimicrobial action of natural bacteriocins and for future exploration of small bio-inspired peptides able to disrupt bacterial membranes.
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Affiliation(s)
- Kamila Riedlová
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 3, 18223 Prague, Czech Republic; Department of Physical and Macromolecular Chemistry, Faculty of Science, Charles University, Hlavova 8, 12800 Prague, Czech Republic
| | - Tereza Dolejšová
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 3, 18223 Prague, Czech Republic; Department of Genetics and Microbiology, Faculty of Science, Charles University, Viničná 5, 12843 Prague, Czech Republic
| | - Radovan Fišer
- Department of Genetics and Microbiology, Faculty of Science, Charles University, Viničná 5, 12843 Prague, Czech Republic.
| | - Lukasz Cwiklik
- J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 3, 18223 Prague, Czech Republic.
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4
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Sofińska K, Lupa D, Chachaj-Brekiesz A, Czaja M, Kobierski J, Seweryn S, Skirlińska-Nosek K, Szymonski M, Wilkosz N, Wnętrzak A, Lipiec E. Revealing local molecular distribution, orientation, phase separation, and formation of domains in artificial lipid layers: Towards comprehensive characterization of biological membranes. Adv Colloid Interface Sci 2022; 301:102614. [PMID: 35190313 DOI: 10.1016/j.cis.2022.102614] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 01/28/2022] [Accepted: 02/01/2022] [Indexed: 01/01/2023]
Abstract
Lipids, together with molecules such as DNA and proteins, are one of the most relevant systems responsible for the existence of life. Selected lipids are able to assembly into various organized structures, such as lipid membranes. The unique properties of lipid membranes determine their complex functions, not only to separate biological environments, but also to participate in regulatory functions, absorption of nutrients, cell-cell communication, endocytosis, cell signaling, and many others. Despite numerous scientific efforts, still little is known about the reason underlying the variability within lipid membranes, and its biochemical significance. In this review, we discuss the structural complexity of lipid membranes, as well as the importance to simplify studied systems in order to understand phenomena occurring in natural, complex membranes. Such systems require a model interface to be analyzed. Therefore, here we focused on analytical studies of artificial systems at various interfaces. The molecular structure of lipid membranes, specifically the nanometric thickens of molecular bilayer, limits in a major extent the choice of highly sensitive methods suitable to study such structures. Therefore, we focused on methods that combine high sensitivity, and/or chemical selectivity, and/or nanometric spatial resolution, such as atomic force microscopy, nanospectroscopy (tip-enhanced Raman spectroscopy, infrared nanospectroscopy), phase modulation infrared reflection-absorption spectroscopy, sum-frequency generation spectroscopy. We summarized experimental and theoretical approaches providing information about molecular structure and composition, lipid spatial distribution (phase separation), organization (domain shape, molecular orientation) of lipid membranes, and real-time visualization of the influence of various molecules (proteins, drugs) on their integrity. An integral part of this review discusses the latest achievements in the field of lipid layer-based biosensors.
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5
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Ulhuq FR, Mariano G. Bacterial pore-forming toxins. MICROBIOLOGY (READING, ENGLAND) 2022; 168:001154. [PMID: 35333704 PMCID: PMC9558359 DOI: 10.1099/mic.0.001154] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 02/03/2022] [Indexed: 12/11/2022]
Abstract
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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Affiliation(s)
- Fatima R. Ulhuq
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Giuseppina Mariano
- Microbes in Health and Disease Theme, Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, UK
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6
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Zhang Y, Zhang HX, Zheng QC. In Silico Study of Membrane Lipid Composition Regulating Conformation and Hydration of Influenza Virus B M2 Channel. J Chem Inf Model 2020; 60:3603-3615. [PMID: 32589410 DOI: 10.1021/acs.jcim.0c00329] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The proton conduction of transmembrane influenza virus B M2 (BM2) proton channel is possibly mediated by the membrane environment, but the detailed molecular mechanism is challenging to determine. In this work, how membrane lipid composition regulates the conformation and hydration of BM2 channel is elucidated in silico. The appearance of several important hydrogen-bond networks has been discovered, as the addition of negatively charged lipid palmitoyloleoyl phosphatidylglycerol (POPG) and cholesterol reduces membrane fluidity and augments membrane rigidity. A more rigid membrane environment is beneficial to expand the channel, allow more water to enter the channel, promote channel hydration, and then even affect the proton conduction facilitated by the hydrated channel. Thus, membrane environment could be identified as an important influence factor of conformation and hydration of BM2. These findings can provide a unique perspective for understanding the mechanism of membrane lipid composition regulating conformation and hydration of BM2 and have important significance to the further study of anti-influenza virus B drugs.
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Affiliation(s)
- Yue Zhang
- Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, International Joint Research Laboratory of Nano-Micro Architecture Chemistry, College of Chemistry, Jilin University, Changchun 130023, People's Republic of China
| | - Hong-Xing Zhang
- Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, International Joint Research Laboratory of Nano-Micro Architecture Chemistry, College of Chemistry, Jilin University, Changchun 130023, People's Republic of China
| | - Qing-Chuan Zheng
- Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, International Joint Research Laboratory of Nano-Micro Architecture Chemistry, College of Chemistry, Jilin University, Changchun 130023, People's Republic of China.,Key Laboratory for Molecular Enzymology and Engineering of the Ministry of Education, Jilin University, Changchun 130023, People's Republic of China
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7
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Liposomal membrane permeability assessment by fluorescence techniques: Main permeabilizing agents, applications and challenges. Int J Pharm 2020; 580:119198. [PMID: 32169353 DOI: 10.1016/j.ijpharm.2020.119198] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 02/19/2020] [Accepted: 03/02/2020] [Indexed: 01/08/2023]
Abstract
Liposomes are lipid vesicles made of one or multiple lipid bilayers surrounding an internal aqueous core. They are broadly employed as models to study membrane structure and properties. Among these properties, liposome membrane permeability is crucial and widely assessed by fluorescence techniques. The first part of this review is devoted to describe the various techniques used for membrane permeability assessment. Attention is paid to fluorescence techniques based on vesicle leakage of self-quenching probes, dye/quencher pair or cation/ligand pair. Secondly, the membrane-active agents inducing membrane permeabilization is presented and details on their mechanisms of action are given. Emphasis is also laid on the intrinsic and extrinsic factors that can modulate the membrane permeability. Hence, a suitable liposomal membrane should be formulated according to the aim of the study and its application.
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8
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Su Z, Ho D, Merrill AR, Lipkowski J. In Situ Electrochemical and PM-IRRAS Studies of Colicin E1 Ion Channels in the Floating Bilayer Lipid Membrane. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:8452-8459. [PMID: 31194562 DOI: 10.1021/acs.langmuir.9b01251] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Colicin E1 is a channel-forming bacteriocin produced by certain Escherichia coli cells in an effort to reduce competition from other bacterial strains. The colicin E1 channel domain was incorporated into a 1,2-diphytanoyl- sn-glycero-3-phosphocholine floating bilayer situated on a 1-thio-?-d-glucose-modified gold (111) surface. The electrochemical properties of the colicin E1 channel in the floating bilayer were measured by electrochemical impedance spectroscopy; the configuration and orientation of colicin E1 in the bilayer were determined by polarization-modulation-infrared-reflection absorption spectroscopy. The EIS and IR results indicate that colicin E1 adopts a closed-channel state at the positive transmembrane potential, leading to high membrane resistance and a large tilt angle of ?-helices. When the transmembrane potential becomes negative, colicin E1 begins to insert into the lipid bilayer, corresponding to low membrane resistance and a low tilt angle of ?-helices. The insertion of colicin E1 into the lipid bilayer is driven by the negative transmembrane potential, and the ion-channel open and closed states are potential reversible. The data in this report provide new insights into the voltage-gated mechanism of colicin E1 ion channels in phospholipid bilayers and illustrate that the floating bilayer lipid membrane at the metal electrode surface is a robust platform to study membrane-active proteins and peptides in a quasi-natural environment.
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9
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Vasilchenko AS, Valyshev AV. Pore-forming bacteriocins: structural–functional relationships. Arch Microbiol 2018; 201:147-154. [DOI: 10.1007/s00203-018-1610-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2018] [Revised: 08/19/2018] [Accepted: 12/11/2018] [Indexed: 12/21/2022]
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10
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On mechanisms of colicin import: the outer membrane quandary. Biochem J 2018; 475:3903-3915. [PMID: 30541793 DOI: 10.1042/bcj20180477] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 11/02/2018] [Accepted: 11/12/2018] [Indexed: 01/09/2023]
Abstract
Current problems in the understanding of colicin import across the Escherichia coli outer membrane (OM), involving a range of cytotoxic mechanisms, are discussed: (I) Crystal structure analysis of colicin E3 (RNAase) with bound OM vitamin B12 receptor, BtuB, and of the N-terminal translocation (T) domain of E3 and E9 (DNAase) inserted into the OM OmpF porin, provide details of the initial interaction of the colicin central receptor (R)- and N-terminal T-domain with OM receptors/translocators. (II) Features of the translocon include: (a) high-affinity (K d ≈ 10-9 M) binding of the E3 receptor-binding R-domain E3 to BtuB; (b) insertion of disordered colicin N-terminal domain into the OmpF trimer; (c) binding of the N-terminus, documented for colicin E9, to the TolB protein on the periplasmic side of OmpF. Reinsertion of the colicin N-terminus into the second of the three pores in OmpF implies a colicin anchor site on the periplasmic side of OmpF. (III) Studies on the insertion of nuclease colicins into the cytoplasmic compartment imply that translocation proceeds via the C-terminal catalytic domain, proposed here to insert through the unoccupied third pore of the OmpF trimer, consistent with in vitro occlusion of OmpF channels by the isolated E3 C-terminal domain. (IV) Discussion of channel-forming colicins focuses mainly on colicin E1 for which BtuB is receptor and the OM TolC protein the proposed translocator. The ability of TolC, part of a multidrug efflux pump, for which there is no precedent for an import function, to provide a trans-periplasmic import pathway for colicin E1, is questioned on the basis of an unfavorable hairpin conformation of colicin N-terminal peptides inserted into TolC.
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11
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Vorob'ev VN, Mirziev SI, Alexandrov EA, Sibgatullin TA. Characteristics of water and ion exchange of Elodea nuttallii cells at high concentrations of lanthanides. CHEMOSPHERE 2016; 165:329-334. [PMID: 27664522 DOI: 10.1016/j.chemosphere.2016.09.044] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 09/09/2016] [Accepted: 09/12/2016] [Indexed: 06/06/2023]
Abstract
Changes of diffusive permeability of membranes of Elodea nuttallii cells following a short-term (60 min) treatment with high concentrations of lanthanides were recorded by the 1H NMR-diffusometry and conductometry methods. The 1-h infiltration of segments of Elodea nuttallii internodes in 10 mM solutions of nitrates of La, Nd and Lu resulted in the increased leakage of electrolytes from cells, but has no effect on a water diffusive permeability of membranes. In samples subjected to a 30 min pretreatment with a water channel inhibitor HgCl2 the water diffusive permeability of membranes (Pd) drops down under the influence of lanthanides, as well as an outcome of electrolytes. To explain the observed effects the change of spontaneous curvature of membrane lipid layer has been taken into consideration. The interaction of lanthanides with lipids of plasmalemma leads to the negative spontaneous curvature of lipid layer at which membrane channels are unclosed. Blocking of the ionic and water channels by mercury ions compensate the effect of change of spontaneous curvature of lipid layer.
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Affiliation(s)
- Vladimir N Vorob'ev
- Kazan Institute of Biochemistry and Biophysics, Kazan Science Center, Russian Academy of Sciences, P.O. Box 30, Lobachevsky st. 2/13, Kazan, 420111, Russia; Kazan (Volga) Federal University, Kremlevsky st. 16, Kazan, 420008, Russia
| | - Samat I Mirziev
- Kazan (Volga) Federal University, Kremlevsky st. 16, Kazan, 420008, Russia
| | | | - Timur A Sibgatullin
- Kazan Institute of Biochemistry and Biophysics, Kazan Science Center, Russian Academy of Sciences, P.O. Box 30, Lobachevsky st. 2/13, Kazan, 420111, Russia.
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12
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Rokitskaya TI, Kotova EA, Naberezhnykh GA, Khomenko VA, Gorbach VI, Firsov AM, Zelepuga EA, Antonenko YN, Novikova OD. Single channel activity of OmpF-like porin from Yersinia pseudotuberculosis. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:883-91. [PMID: 26854962 DOI: 10.1016/j.bbamem.2016.02.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Revised: 01/28/2016] [Accepted: 02/04/2016] [Indexed: 11/16/2022]
Abstract
To gain a mechanistic insight in the functioning of the OmpF-like porin from Yersinia pseudotuberculosis (YOmpF), we compared the effect of pH variation on the ion channel activity of the protein in planar lipid bilayers and its binding to lipid membranes. The behavior of YOmpF channels upon acidification was similar to that previously described for Escherichia coli OmpF. In particular, a decrease in pH of the bathing solution resulted in a substantial reduction of YOmpF single channel conductance, accompanied by the emergence of subconductance states. Similar subconductance substates were elicited by the addition of lysophosphatidylcholine. This observation, made with porin channels for the first time, pointed to the relevance of lipid-protein interactions, in particular, the lipid curvature stress, to the appearance of subconductance states at acidic pH. Binding of YOmpF to membranes displayed rather modest dependence on pH, whereas the channel-forming potency of the protein tremendously decreased upon acidification.
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Affiliation(s)
- Tatyana I Rokitskaya
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory 1/40, Moscow 119991, Russia
| | - Elena A Kotova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory 1/40, Moscow 119991, Russia
| | - Gennadiy A Naberezhnykh
- Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, Prospect 100 let Vladivostoku 159, Vladivostok 690022, Russia
| | - Valentina A Khomenko
- Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, Prospect 100 let Vladivostoku 159, Vladivostok 690022, Russia
| | - Vladimir I Gorbach
- Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, Prospect 100 let Vladivostoku 159, Vladivostok 690022, Russia
| | - Alexander M Firsov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory 1/40, Moscow 119991, Russia; Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Leninskie Gory 1/73, Moscow 119991, Russia
| | - Elena A Zelepuga
- Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, Prospect 100 let Vladivostoku 159, Vladivostok 690022, Russia
| | - Yuri N Antonenko
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory 1/40, Moscow 119991, Russia.
| | - Olga D Novikova
- Elyakov Pacific Institute of Bioorganic Chemistry, Far Eastern Branch, Russian Academy of Sciences, Prospect 100 let Vladivostoku 159, Vladivostok 690022, Russia.
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13
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Whitlock JM, Hartzell HC. A Pore Idea: the ion conduction pathway of TMEM16/ANO proteins is composed partly of lipid. Pflugers Arch 2016; 468:455-73. [PMID: 26739711 PMCID: PMC4751199 DOI: 10.1007/s00424-015-1777-2] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Revised: 12/14/2015] [Accepted: 12/16/2015] [Indexed: 01/04/2023]
Abstract
Since their first descriptions, ion channels have been conceived as proteinaceous conduits that facilitate the passage of ionic cargo between segregated environments. This concept is reinforced by crystallographic structures of cation channels depicting ion conductance pathways completely lined by protein. Although lipids are sometimes present in fenestrations near the pore or may be involved in channel gating, there is little or no evidence that lipids inhabit the ion conduction pathway. Indeed, the presence of lipid acyl chains in the conductance pathway would curse the design of the channel's aqueous pore. Here, we make a speculative proposal that anion channels in the TMEM16/ANO superfamily have ion conductance pathways composed partly of lipids. Our reasoning is based on the idea that TMEM16 ion channels evolved from a kind of lipid transporter that scrambles lipids between leaflets of the membrane bilayer and the modeled structural similarity between TMEM16 lipid scramblases and TMEM16 anion channels. This novel view of the TMEM16 pore offers explanation for the biophysical and pharmacological oddness of TMEM16A. We build upon the recent X-ray structure of nhTMEM16 and develop models of both TMEM16 ion channels and lipid scramblases to bolster our proposal. It is our hope that this model of the TMEM16 pore will foster innovative investigation into TMEM16 function.
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Affiliation(s)
- Jarred M Whitlock
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - H Criss Hartzell
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA.
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14
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Gilbert RJC. Protein-lipid interactions and non-lamellar lipidic structures in membrane pore formation and membrane fusion. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:487-99. [PMID: 26654785 DOI: 10.1016/j.bbamem.2015.11.026] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Revised: 10/23/2015] [Accepted: 11/30/2015] [Indexed: 12/27/2022]
Abstract
Pore-forming proteins and peptides act on their targeted lipid bilayer membranes to increase permeability. This approach to the modulation of biological function is relevant to a great number of living processes, including; infection, parasitism, immunity, apoptosis, development and neurodegeneration. While some pore-forming proteins/peptides assemble into rings of subunits to generate discrete, well-defined pore-forming structures, an increasing number is recognised to form pores via mechanisms which co-opt membrane lipids themselves. Among these, membrane attack complex-perforin/cholesterol-dependent cytolysin (MACPF/CDC) family proteins, Bax/colicin family proteins and actinoporins are especially prominent and among the mechanisms believed to apply are the formation of non-lamellar (semi-toroidal or toroidal) lipidic structures. In this review I focus on the ways in which lipids contribute to pore formation and contrast this with the ways in which lipids are co-opted also in membrane fusion and fission events. A variety of mechanisms for pore formation that involve lipids exists, but they consistently result in stable hybrid proteolipidic structures. These structures are stabilised by mechanisms in which pore-forming proteins modify the innate capacity of lipid membranes to respond to their environment, changing shape and/or phase and binding individual lipid molecules directly. In contrast, and despite the diversity in fusion protein types, mechanisms for membrane fusion are rather similar to each other, mapping out a pathway from pairs of separated compartments to fully confluent fused membranes. Fusion proteins generate metastable structures along the way which, like long-lived proteolipidic pore-forming complexes, rely on the basic physical properties of lipid bilayers. Membrane fission involves similar intermediates, in the reverse order. I conclude by considering the possibility that at least some pore-forming and fusion proteins are evolutionarily related homologues. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Mauro Dalla Serra and Franco Gambale.
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Affiliation(s)
- Robert J C Gilbert
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK.
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15
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Largo E, Verdiá-Báguena C, Aguilella VM, Nieva JL, Alcaraz A. Ion channel activity of the CSFV p7 viroporin in surrogates of the ER lipid bilayer. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:30-7. [PMID: 26464198 PMCID: PMC7094309 DOI: 10.1016/j.bbamem.2015.10.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 10/08/2015] [Accepted: 10/09/2015] [Indexed: 12/22/2022]
Affiliation(s)
- Eneko Largo
- Biophysics Unit (CSIC, UPV/EHU), Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain
| | - Carmina Verdiá-Báguena
- Laboratory of Molecular Biophysics, Department of Physics, University Jaume I, 12071 Castellón, Spain
| | - Vicente M Aguilella
- Laboratory of Molecular Biophysics, Department of Physics, University Jaume I, 12071 Castellón, Spain
| | - José L Nieva
- Biophysics Unit (CSIC, UPV/EHU), Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain
| | - Antonio Alcaraz
- Laboratory of Molecular Biophysics, Department of Physics, University Jaume I, 12071 Castellón, Spain.
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16
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Peroxidative permeabilization of liposomes induced by cytochrome c/cardiolipin complex. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:767-74. [DOI: 10.1016/j.bbamem.2014.11.027] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 11/21/2014] [Accepted: 11/25/2014] [Indexed: 01/23/2023]
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17
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Triatoma virus recombinant VP4 protein induces membrane permeability through dynamic pores. J Virol 2015; 89:4645-54. [PMID: 25673713 DOI: 10.1128/jvi.00011-15] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
UNLABELLED In naked viruses, membrane breaching is a key step that must be performed for genome transfer into the target cells. Despite its importance, the mechanisms behind this process remain poorly understood. The small protein VP4, encoded by the genomes of most viruses of the order Picornavirales, has been shown to be involved in membrane alterations. Here we analyzed the permeabilization activity of the natively nonmyristoylated VP4 protein from triatoma virus (TrV), a virus belonging to the Dicistroviridae family within the Picornavirales order. The VP4 protein was produced as a C-terminal maltose binding protein (MBP) fusion to achieve its successful expression. This recombinant VP4 protein is able to produce membrane permeabilization in model membranes in a membrane composition-dependent manner. The induced permeability was also influenced by the pH, being greater at higher pH values. We demonstrate that the permeabilization activity elicited by the protein occurs through discrete pores that are inserted on the membrane. Sizing experiments using fluorescent dextrans, cryo-electron microscopy imaging, and other, additional techniques showed that recombinant VP4 forms heterogeneous proteolipidic pores rather than common proteinaceous channels. These results suggest that the VP4 protein may be involved in the membrane alterations required for genome transfer or cell entry steps during dicistrovirus infection. IMPORTANCE During viral infection, viruses need to overcome the membrane barrier in order to enter the cell and replicate their genome. In nonenveloped viruses membrane fusion is not possible, and hence, other mechanisms are implemented. Among other proteins, like the capsid-forming proteins and the proteins required for viral replication, several viruses of the order Picornaviridae contain a small protein called VP4 that has been shown to be involved in membrane alterations. Here we show that the triatoma virus VP4 protein is able to produce membrane permeabilization in model membranes by the formation of heterogeneous dynamic pores. These pores formed by VP4 may be involved in the genome transfer or cell entry steps during viral infection.
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18
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Modifiers of membrane dipole potentials as tools for investigating ion channel formation and functioning. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2015; 315:245-97. [PMID: 25708465 DOI: 10.1016/bs.ircmb.2014.12.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Electrostatic fields generated on and within biological membranes play a fundamental role in key processes in cell functions. The role of the membrane dipole potential is of particular interest because of its powerful impact on membrane permeability and lipid-protein interactions, including protein insertion, oligomerization, and function. The membrane dipole potential is defined by the orientation of electric dipoles of lipid headgroups, fatty acid carbonyl groups, and membrane-adsorbed water. As a result, the membrane interior is several hundred millivolts more positive than the external aqueous phase. This potential decrease depends on the lipid, and especially sterol, composition of the membrane. The adsorption of certain electroneutral molecules known as dipole modifiers may also lead to significant changes in the magnitude of the potential decrease. These agents are widely used to study the effects of the dipole potential on membrane transport. This review presents a critical analysis of a variety of data from studies dedicated to ion channel formation and functioning in membranes with different dipole potentials. The types of ion channels found in cellular membranes and pores formed by antimicrobial agents and toxins in artificial lipid membranes are summarized. The mechanisms underlying the influence of the membrane dipole potential on ion channel activity, including dipole-dipole and charge-dipole interactions in the pores and in membranes, are discussed. A hypothesis, in which lipid rafts in both model and cellular membranes also modulate ion channel activity by virtue of an increased or decreased dipole potential, is also considered.
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19
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Gilbert RJ, Serra MD, Froelich CJ, Wallace MI, Anderluh G. Membrane pore formation at protein–lipid interfaces. Trends Biochem Sci 2014; 39:510-6. [DOI: 10.1016/j.tibs.2014.09.002] [Citation(s) in RCA: 125] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Revised: 09/13/2014] [Accepted: 09/15/2014] [Indexed: 11/15/2022]
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20
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Chulkov EG, Schagina LV, Ostroumova OS. Membrane dipole modifiers modulate single-length nystatin channels via reducing elastic stress in the vicinity of the lipid mouth of a pore. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1848:192-9. [PMID: 25223717 DOI: 10.1016/j.bbamem.2014.09.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2014] [Revised: 08/13/2014] [Accepted: 09/08/2014] [Indexed: 10/24/2022]
Abstract
The polyene antifungal antibiotic nystatin confers its biological activity by forming pores in the membranes of target cells. Exposure of only one side of the membrane to nystatin is more relevant than two-side exposure because in vivo antibiotic molecules initially interact with cell membrane from the exterior side. The effect of flavonoids and styryl dyes on the steady-state conductance induced by a cis-side addition of nystatin was investigated by using electrophysiological measurements on artificial membranes. The assessment of changes in membrane dipole potential by dipole modifiers was carried out by their influence on K(+)-nonactin (K(+)-valinomycin) current. The alterations of the phase segregation scenario induced by nystatin and flavonoids were observed via confocal fluorescence microscopy. The introduction of phloretin, phlorizin, biochanin A, myricetin, quercetin, taxifolin, genistin, genistein, and RH 421 leads to a significant increase in the nystatin-induced steady-state transmembrane current through membranes composed of a mixture of DOPC, cholesterol and sphingomyelin (57:33:10 mol%). Conversely, daidzein, catechin, trihydroxyacetophenone, and RH 237 do not affect the transmembrane current. Three possible mechanisms that explain the observed results are discussed: changes in the membrane dipole potential, alterations of the phase separation within the lipid bilayer, and influences of the dipole modifiers on the formation of the lipid mouth of the polyene pore. Most likely, changes in the monolayer curvature in the vicinity of trans-mouth of a nystatin single-length channel prevail over alterations of dipole potential of membrane and the phase segregation scenarios induced by dipole modifiers.
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Affiliation(s)
- Evgeny G Chulkov
- Institute of Cytology of the Russian Academy of Sciences, Tikhoretsky Ave. 4, St. Petersburg 194064, Russia.
| | - Ludmila V Schagina
- Institute of Cytology of the Russian Academy of Sciences, Tikhoretsky Ave. 4, St. Petersburg 194064, Russia
| | - Olga S Ostroumova
- Institute of Cytology of the Russian Academy of Sciences, Tikhoretsky Ave. 4, St. Petersburg 194064, Russia
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21
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Perforin oligomers form arcs in cellular membranes: a locus for intracellular delivery of granzymes. Cell Death Differ 2014; 22:74-85. [PMID: 25146929 DOI: 10.1038/cdd.2014.110] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Revised: 07/01/2014] [Accepted: 07/03/2014] [Indexed: 01/28/2023] Open
Abstract
Perforin-mediated cytotoxicity is an essential host defense, in which defects contribute to tumor development and pathogenic disorders including autoimmunity and autoinflammation. How perforin (PFN) facilitates intracellular delivery of pro-apoptotic and inflammatory granzymes across the bilayer of targets remains unresolved. Here we show that cellular susceptibility to granzyme B (GzmB) correlates with rapid PFN-induced phosphatidylserine externalization, suggesting that pores are formed at a protein-lipid interface by incomplete membrane oligomers (or arcs). Supporting a role for these oligomers in protease delivery, an anti-PFN antibody (pf-80) suppresses necrosis but increases phosphatidylserine flip-flop and GzmB-induced apoptosis. As shown by atomic force microscopy on planar bilayers and deep-etch electron microscopy on mammalian cells, pf-80 increases the proportion of arcs which correlates with the presence of smaller electrical conductances, while large cylindrical pores decline. PFN appears to form arc structures on target membranes that serve as minimally disrupting conduits for GzmB translocation. The role of these arcs in PFN-mediated pathology warrants evaluation where they may serve as novel therapeutic targets.
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Abstract
Bacteria secrete and harbor in their membranes a number of pore-forming proteins. Some of these are bona fide ion channels that may respond to changes in membrane tension, voltage, or pH. Others may be large translocons used for the secretion of folded or unfolded polypeptide substrates. Additionally, many secreted toxins insert into target cell membranes and form pores that either collapse membrane electrochemical gradients or provide conduits for the delivery of virulence factors. In all cases, electrophysiological approaches have yielded much progress in past decades in understanding the functional mechanisms of these pores. By monitoring the changes in current due to ion flow through the pores, these techniques are used as high-resolution tools to gather detailed information on the kinetic and permeation properties of these proteins, including those whose physiological role is not ion flux. This review highlights some of the electrophysiological studies that have advanced the field of transport by pore-forming proteins of bacterial origin.
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Affiliation(s)
- Anne H Delcour
- Department of Biology and Biochemistry, University of Houston, Houston, Texas 77204-5001;
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23
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Abstract
Membrane proteins are generally divided into two classes. Integral proteins span the lipid bilayer, and peripheral proteins are located at the membrane surface. Here, we provide evidence for membrane proteins of a third class that stabilize lipid pores, most probably as toroidal structures. We examined mutants of the staphylococcal α-hemolysin pore so severely truncated that the protein cannot span a bilayer. Nonetheless, the doughnut-like structures elicited well-defined transmembrane ionic currents by inducing pore formation in the underlying lipids. The formation of lipid pores, produced here by a structurally defined protein, is supported by the lipid and voltage dependences of pore formation, and by molecular dynamics simulations. We discuss the role of stabilized lipid pores in amyloid disease, the action of antimicrobial peptides, and the assembly of the membrane-attack complexes of the immune system.
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24
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Snyder AB, Worobo RW. Chemical and genetic characterization of bacteriocins: antimicrobial peptides for food safety. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2014; 94:28-44. [PMID: 23818338 DOI: 10.1002/jsfa.6293] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 06/24/2013] [Accepted: 07/01/2013] [Indexed: 05/16/2023]
Abstract
Antimicrobial peptides are produced across all domains of life. Among these diverse compounds, those produced by bacteria have been most successfully applied as agents of biocontrol in food and agriculture. Bacteriocins are ribosomally synthesized, proteinaceous compounds that inhibit the growth of closely related bacteria. Even within the subcategory of bacteriocins, the peptides vary significantly in terms of the gene cluster responsible for expression, and chemical and structural composition. The polycistronic gene cluster generally includes a structural gene and various combinations of immunity, secretion, and regulatory genes and modifying enzymes. Chemical variation can exist in amino acid identity, chain length, secondary and tertiary structural features, as well as specificity of active sites. This diversity posits bacteriocins as potential antimicrobial agents with a range of functions and applications. Those produced by food-grade bacteria and applied in normally occurring concentrations can be used as GRAS-status food additives. However, successful application requires thorough characterization.
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Affiliation(s)
- Abigail B Snyder
- Department of Food Science, Cornell University, Geneva, NY, 14456, USA
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25
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Abstract
The cell membrane is crucial for protection of the cell from its environment. MACPF/CDC proteins are a large superfamily known to be essential for bacterial pathogenesis and proper functioning of the immune system. The three most studied groups of MACPF/CDC proteins are cholesterol-dependent cytolysins from bacteria, the membrane attack complex of complement and human perforin. Their primary function is to form transmembrane pores in target cell membranes. The common mechanism of action comprises water-soluble monomeric proteins binding to the host cell membrane, oligomerization, and formation of a functional pore. This causes a disturbance in gradients of ions and other molecules across the membrane and can lead to cell death. Cells react to this form of attack in a complex manner. Responses can be general, like removing the perforated part of the membrane, or more specific, in many cases depending on binding of proteins to specific receptors to trigger various signalling cascades.
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26
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Aguilella VM, Verdiá-Báguena C, Alcaraz A. Lipid charge regulation of non-specific biological ion channels. Phys Chem Chem Phys 2014; 16:3881-93. [DOI: 10.1039/c3cp54690j] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Lipid charge regulation effects in different protein–lipid conformations highlight the role of electrostatic interactions in conductance and selectivity of non-specific biological ion channels.
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Affiliation(s)
| | | | - Antonio Alcaraz
- Dept. Physics
- Lab. Molecular Biophysics
- Universitat Jaume I
- 12080 Castellón, Spain
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27
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Wager B, Faudry E, Wills T, Attree I, Delcour AH. Current fluctuation analysis of the PopB and PopD translocon components of the Pseudomonas aeruginosa type III secretion system. Biophys J 2013; 104:1445-55. [PMID: 23561521 DOI: 10.1016/j.bpj.2013.02.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Revised: 02/05/2013] [Accepted: 02/12/2013] [Indexed: 12/24/2022] Open
Abstract
Pseudomonas aeruginosa is a major agent of hospital-acquired infections, and a pathogen of immunocompromised, cystic fibrosis and burn patients. It uses a type III secretion system for the injection of toxins directly into host cells, through a translocon assembled in the host cell membrane. The hydrophobic translocator subunits of this system, PopB and PopD, have membrane permeabilizing activity based on previous dye leakage experiments, but little is known about the mechanism of assembly and the pore properties of this translocon. Using electrophysiology, we have observed that an equimolar mixture of PopB and PopD induces current fluctuations in planar lipid bilayers, with a unitary conductance of 57 pS in 1 M KCl and numerous larger conductance levels. The activity depends on voltage magnitude and polarity, and increases with protein concentration and the duration of the voltage step. PopB alone is sufficient for producing current fluctuations. PopD rarely displays any transitions, but accelerates PopB onset of activity. The effects of pH, ionic strength, and lipid composition have also been explored. Our data provide new, to our knowledge, insights into the behavior of PopB and PopD by highlighting similarities with secreted pore-forming peptides, and by suggesting that PopB/PopD may form channels via the toroidal pore model. We believe that the events we report here represent the initial steps of insertion and assembly of these translocators in the membrane.
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Affiliation(s)
- Beau Wager
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, USA
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28
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Raghava S, Giorda KM, Romano FB, Heuck AP, Hebert DN. SV40 late protein VP4 forms toroidal pores to disrupt membranes for viral release. Biochemistry 2013; 52:3939-48. [PMID: 23651212 DOI: 10.1021/bi400036z] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Nonenveloped viruses are generally released from the cell by the timely lysis of host cell membranes. SV40 has been used as a model virus for the study of the lytic nonenveloped virus life cycle. The expression of SV40 VP4 at later times during infection is concomitant with cell lysis. To investigate the role of VP4 in viral release and its mechanism of action, VP4 was expressed and purified from bacteria as a fusion protein for use in membrane disruption assays. Purified VP4 perforated membranes as demonstrated by the release of fluorescent markers encapsulated within large unilamellar vesicles or liposomes. Dynamic light scattering results revealed that VP4 treatment did not cause membrane lysis or change the size of the liposomes. Liposomes encapsulated with 4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-3-indacene-labeled streptavidin were used to show that VP4 formed stable pores in membranes. These VP4 pores had an inner diameter of 1-5 nm. Asymmetrical liposomes containing pyrene-labeled lipids in the outer monolayer were employed to monitor transbilayer lipid diffusion. Consistent with VP4 forming toroidal pore structures in membranes, VP4 induced transbilayer lipid diffusion or lipid flip-flop. Altogether, these studies support a central role for VP4 acting as a viroporin in the disruption of cellular membranes to trigger SV40 viral release by forming toroidal pores that unite the outer and inner leaflets of membrane bilayers.
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Affiliation(s)
- Smita Raghava
- Department of Biochemistry and Molecular Biology, University of Massachusetts , 710 North Pleasant Street, Amherst, Massachusetts 01003, United States
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29
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Analysis of SARS-CoV E protein ion channel activity by tuning the protein and lipid charge. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1828:2026-31. [PMID: 23688394 PMCID: PMC3715572 DOI: 10.1016/j.bbamem.2013.05.008] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 04/24/2013] [Accepted: 05/09/2013] [Indexed: 11/30/2022]
Abstract
A partial characterization of the ion channels formed by the SARS coronavirus (CoV) envelope (E) protein was previously reported (C. Verdiá-Báguena et al., 2012 [12]). Here, we provide new significant insights on the involvement of lipids in the structure and function of the CoV E protein channel on the basis of three series of experiments. First, reversal potential measurements over a wide range of pH allow the dissection of the contributions to channel selectivity coming from ionizable residues of the protein transmembrane domain and also from the negatively charged groups of diphytanoyl phosphatidylserine (DPhPS) lipid. The corresponding effective pKas are consistent with the model pKas of the acidic residue candidates for titration. Second, the change of channel conductance with salt concentration reveals two distinct regimes (Donnan-controlled electrodiffusion and bulk-like electrodiffusion) fully compatible with the outcomes of selectivity experiments. Third, by measuring channel conductance in mixtures of neutral diphytanoyl phosphatidylcholine (DPhPC) lipids and negatively charged DPhPS lipids in low and high salt concentrations we conclude that the protein–lipid conformation in the channel is likely the same in charged and neutral lipids. Overall, the whole set of experiments supports the proteolipidic structure of SARS-CoV E channels and explains the large difference in channel conductance observed between neutral and charged membranes. SARS-CoV E protein channel structure is analyzed by tuning lipid charge. Proteolipidic channel conformation is similar in charged and neutral lipids. Lipid charge modulation of conductance is biphasic.
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30
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Lee DK, Brender JR, Sciacca MFM, Krishnamoorthy J, Yu C, Ramamoorthy A. Lipid composition-dependent membrane fragmentation and pore-forming mechanisms of membrane disruption by pexiganan (MSI-78). Biochemistry 2013; 52:3254-63. [PMID: 23590672 DOI: 10.1021/bi400087n] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The potency and selectivity of many antimicrobial peptides (AMPs) are correlated with their ability to interact with and disrupt the bacterial cell membrane. In vitro experiments using model membranes have been used to determine the mechanism of membrane disruption of AMPs. Because the mechanism of action of an AMP depends on the ability of the model membrane to accurately mimic the cell membrane, it is important to understand the effect of membrane composition. Anionic lipids that are present in the outer membrane of prokaryotes but are less common in eukaryotic membranes are usually thought to be key for the bacterial selectivity of AMPs. We show by fluorescence measurements of peptide-induced membrane permeabilization that the presence of anionic lipids at high concentrations can actually inhibit membrane disruption by the AMP MSI-78 (pexiganan), a representative of a large class of highly cationic AMPs. Paramagnetic quenching studies suggest MSI-78 is in a surface-associated inactive mode in anionic sodium dodecyl sulfate micelles but is in a deeply buried and presumably more active mode in zwitterionic dodecylphosphocholine micelles. Furthermore, a switch in mechanism occurs with lipid composition. Membrane fragmentation with MSI-78 can be observed in mixed vesicles containing both anionic and zwitterionic lipids but not in vesicles composed of a single lipid of either type. These findings suggest membrane affinity and membrane permeabilization are not always correlated, and additional effects that may be more reflective of the actual cellular environment can be seen as the complexity of the model membranes is increased.
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Affiliation(s)
- Dong-Kuk Lee
- Departments of Biophysics and Chemistry, University of Michigan , Ann Arbor, Michigan 48109-1055, United States
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31
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Mapingire OS, Wager B, Delcour AH. Electrophysiological characterization of bacterial pore-forming proteins in planar lipid bilayers. Methods Mol Biol 2013; 966:381-396. [PMID: 23299748 DOI: 10.1007/978-1-62703-245-2_24] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Together with patch-clamp, the planar lipid bilayer technique is one of the electrophysiological approaches used to study the biophysical properties of bacterial pore-forming proteins. Electrophysiological studies have provided important insight into the mechanistic details underlying the function of this class of proteins. Although there are different apparatus designs and variations to the process of obtaining channel recordings, the general architecture of a planar lipid bilayer setup involves two compartments filled with an ionic solution and separated by a septum with a micro-aperture, where a phospholipid bilayer is formed, and an amplifier used to clamp the membrane potential and record currents. Bacterial outer membrane porins and translocons, among others, can be reconstituted in this bilayer and their electrophysiology probed in different physicochemical conditions or through functional assays with substrates or potential modulators. This chapter describes specifically the reconstitution of detergent purified outer membrane pore-forming proteins into artificial lipid membranes using a laboratory customized planar lipid bilayer apparatus and the subsequent recording of channel activity under voltage clamp.
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Affiliation(s)
- Owen S Mapingire
- Department of Biology and Biochemistry, University of Houston, Houston, TX, USA
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32
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Affiliation(s)
| | - Sergey M. Bezrukov
- Program in Physical Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, U.S.A
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33
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Balleza D. Mechanical properties of lipid bilayers and regulation of mechanosensitive function: from biological to biomimetic channels. Channels (Austin) 2012; 6:220-33. [PMID: 22790280 DOI: 10.4161/chan.21085] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Material properties of lipid bilayers, including thickness, intrinsic curvature and compressibility regulate the function of mechanosensitive (MS) channels. This regulation is dependent on phospholipid composition, lateral packing and organization within the membrane. Therefore, a more complete framework to understand the functioning of MS channels requires insights into bilayer structure, thermodynamics and phospholipid structure, as well as lipid-protein interactions. Phospholipids and MS channels interact with each other mainly through electrostatic forces and hydrophobic matching, which are also crucial for antimicrobial peptides. They are excellent models for studying the formation and stabilization of membrane pores. Importantly, they perform equivalent responses as MS channels: (1) tilting in response to tension and (2) dissipation of osmotic gradients. Lessons learned from pore forming peptides could enrich our knowledge of mechanisms of action and evolution of these channels. Here, the current state of the art is presented and general principles of membrane regulation of mechanosensitive function are discussed.
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Affiliation(s)
- Daniel Balleza
- Unidad de Biofísica, CSIC, UPV/EHU, Universidad del País Vasco, Leioa, Spain.
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34
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Metkar SS, Wang B, Catalan E, Anderluh G, Gilbert RJC, Pardo J, Froelich CJ. Perforin rapidly induces plasma membrane phospholipid flip-flop. PLoS One 2011; 6:e24286. [PMID: 21931672 PMCID: PMC3171411 DOI: 10.1371/journal.pone.0024286] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Accepted: 08/02/2011] [Indexed: 11/18/2022] Open
Abstract
The cytotoxic cell granule secretory pathway is essential for host defense. This pathway is fundamentally a form of intracellular protein delivery where granule proteases (granzymes) from cytotoxic lymphocytes are thought to diffuse through barrel stave pores generated in the plasma membrane of the target cell by the pore forming protein perforin (PFN) and mediate apoptotic as well as additional biological effects. While recent electron microscopy and structural analyses indicate that recombinant PFN oligomerizes to form pores containing 20 monomers (20 nm) when applied to liposomal membranes, these pores are not observed by propidium iodide uptake in target cells. Instead, concentrations of human PFN that encourage granzyme-mediated apoptosis are associated with pore structures that unexpectedly favor phosphatidylserine flip-flop measured by Annexin-V and Lactadherin. Efforts that reduce PFN mediated Ca influx in targets did not reduce Annexin-V reactivity. Antigen specific mouse CD8 cells initiate a similar rapid flip-flop in target cells. A lipid that augments plasma membrane curvature as well as cholesterol depletion in target cells enhance flip-flop. Annexin-V staining highly correlated with apoptosis after Granzyme B (GzmB) treatment. We propose the structures that PFN oligomers form in the membrane bilayer may include arcs previously observed by electron microscopy and that these unusual structures represent an incomplete mixture of plasma membrane lipid and PFN oligomers that may act as a flexible gateway for GzmB to translocate across the bilayer to the cytosolic leaflet of target cells.
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Affiliation(s)
- Sunil S. Metkar
- Department of Medicine, NorthShore University HealthSystems Research Institute, Evanston, Illinois, United States of America
| | - Baikun Wang
- Department of Medicine, NorthShore University HealthSystems Research Institute, Evanston, Illinois, United States of America
| | - Elena Catalan
- Departamento Bioquimica y Biologia Molecular y Cellular, University of Zaragoza, Zaragoza, Spain
| | - Gregor Anderluh
- Department of Biology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Robert J. C. Gilbert
- Division of Structural Biology, Henry Wellcome Building for Genomic Medicine, Oxford, United Kingdom
| | - Julian Pardo
- Departamento Bioquimica y Biologia Molecular y Cellular, University of Zaragoza, Zaragoza, Spain
- Fundación Aragón I+D, Zaragoza, Spain
| | - Christopher J. Froelich
- Department of Medicine, NorthShore University HealthSystems Research Institute, Evanston, Illinois, United States of America
- * E-mail:
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35
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Mitochondrial ceramide-rich macrodomains functionalize Bax upon irradiation. PLoS One 2011; 6:e19783. [PMID: 21695182 PMCID: PMC3113798 DOI: 10.1371/journal.pone.0019783] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2010] [Accepted: 04/15/2011] [Indexed: 11/19/2022] Open
Abstract
Background Evidence indicates that Bax functions as a “lipidic” pore to regulate mitochondrial outer membrane permeabilization (MOMP), the apoptosis commitment step, through unknown membrane elements. Here we show mitochondrial ceramide elevation facilitates MOMP-mediated cytochrome c release in HeLa cells by generating a previously-unrecognized mitochondrial ceramide-rich macrodomain (MCRM), which we visualize and isolate, into which Bax integrates. Methodology/Principal Findings MCRMs, virtually non-existent in resting cells, form upon irradiation coupled to ceramide synthase-mediated ceramide elevation, optimizing Bax insertion/oligomerization and MOMP. MCRMs are detected by confocal microscopy in intact HeLa cells and isolated biophysically as a light membrane fraction from HeLa cell lysates. Inhibiting ceramide generation using a well-defined natural ceramide synthase inhibitor, Fumonisin B1, prevented radiation-induced Bax insertion, oligomerization and MOMP. MCRM deconstruction using purified mouse hepatic mitochondria revealed ceramide alone is non-apoptogenic. Rather Bax integrates into MCRMs, oligomerizing therein, conferring 1–2 log enhanced cytochrome c release. Consistent with this mechanism, MCRM Bax isolates as high molecular weight “pore-forming” oligomers, while non-MCRM membrane contains exclusively MOMP-incompatible monomeric Bax. Conclusions/Significance Our recent studies in the C. elegans germline indicate that mitochondrial ceramide generation is obligate for radiation-induced apoptosis, although a mechanism for ceramide action was not delineated. Here we demonstrate that ceramide, generated in the mitochondrial outer membrane of mammalian cells upon irradiation, forms a platform into which Bax inserts, oligomerizes and functionalizes as a pore. We posit conceptualization of ceramide as a membrane-based stress calibrator, driving membrane macrodomain organization, which in mitochondria regulates intensity of Bax-induced MOMP, and is pharmacologically tractable in vitro and in vivo.
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Landeta O, Landajuela A, Gil D, Taneva S, DiPrimo C, Sot B, Valle M, Frolov VA, Basañez G. Reconstitution of proapoptotic BAK function in liposomes reveals a dual role for mitochondrial lipids in the BAK-driven membrane permeabilization process. J Biol Chem 2011; 286:8213-8230. [PMID: 21196599 PMCID: PMC3048708 DOI: 10.1074/jbc.m110.165852] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2010] [Revised: 12/18/2010] [Indexed: 12/11/2022] Open
Abstract
BAK is a key effector of mitochondrial outer membrane permeabilization (MOMP) whose molecular mechanism of action remains to be fully dissected in intact cells, mainly due to the inherent complexity of the intracellular apoptotic machinery. Here we show that the core features of the BAK-driven MOMP pathway can be reproduced in a highly simplified in vitro system consisting of recombinant human BAK lacking the carboxyl-terminal 21 residues (BAKΔC) and tBID in combination with liposomes bearing an appropriate lipid environment. Using this minimalist reconstituted system we established that tBID suffices to trigger BAKΔC membrane insertion, oligomerization, and pore formation. Furthermore, we demonstrate that tBID-activated BAKΔC permeabilizes the membrane by forming structurally dynamic pores rather than a large proteinaceous channel of fixed size. We also identified two distinct roles played by mitochondrial lipids along the molecular pathway of BAKΔC-induced membrane permeabilization. First, using several independent approaches, we showed that cardiolipin directly interacts with BAKΔC, leading to a localized structural rearrangement in the protein that "primes" BAKΔC for interaction with tBID. Second, we provide evidence that selected curvature-inducing lipids present in mitochondrial membranes specifically modulate the energetic expenditure required to create the BAKΔC pore. Collectively, our results support the notion that BAK functions as a direct effector of MOMP akin to BAX and also adds significantly to the growing evidence indicating that mitochondrial membrane lipids are actively implicated in BCL-2 protein family function.
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Affiliation(s)
- Olatz Landeta
- From the Unidad de Biofísica (Centro Mixto Consejo Superior de Investigaciones Cientificas-Universidad del Pais Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain
| | - Ane Landajuela
- From the Unidad de Biofísica (Centro Mixto Consejo Superior de Investigaciones Cientificas-Universidad del Pais Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain
| | - David Gil
- CIC-BIOGUNE Structural Biology Unit, Parque Tecnologico Zamudio, Bizkaia, 48160 Derio, Spain
| | - Stefka Taneva
- From the Unidad de Biofísica (Centro Mixto Consejo Superior de Investigaciones Cientificas-Universidad del Pais Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain
| | - Carmelo DiPrimo
- Université de Bordeaux, INSERM U869, Institut Européen de Chimie et de Biologie, Pessac F-33607, France, and
| | - Begoña Sot
- the MRC Centre for Protein Engineering and MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, United Kingdom
| | - Mikel Valle
- CIC-BIOGUNE Structural Biology Unit, Parque Tecnologico Zamudio, Bizkaia, 48160 Derio, Spain
| | - Vadim A Frolov
- From the Unidad de Biofísica (Centro Mixto Consejo Superior de Investigaciones Cientificas-Universidad del Pais Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain,; the Departamento de Bioquímica y Biología Molecular, UPV/EHU, Leioa 48940, Spain,; Ikerbasque, Basque Foundation for Science, 48011 Bilbao, Spain
| | - Gorka Basañez
- From the Unidad de Biofísica (Centro Mixto Consejo Superior de Investigaciones Cientificas-Universidad del Pais Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), P.O. Box 644, 48080 Bilbao, Spain,.
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Westphal D, Dewson G, Czabotar PE, Kluck RM. Molecular biology of Bax and Bak activation and action. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1813:521-31. [PMID: 21195116 DOI: 10.1016/j.bbamcr.2010.12.019] [Citation(s) in RCA: 378] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 12/17/2010] [Accepted: 12/19/2010] [Indexed: 12/26/2022]
Abstract
Bax and Bak are two nuclear-encoded proteins present in higher eukaryotes that are able to pierce the mitochondrial outer membrane to mediate cell death by apoptosis. Thus, organelles recruited by nucleated cells to supply energy can be recruited by Bax and Bak to kill cells. The two proteins lie in wait in healthy cells where they adopt a globular α-helical structure, seemingly as monomers. Following a variety of stress signals, they convert into pore-forming proteins by changing conformation and assembling into oligomeric complexes in the mitochondrial outer membrane. Proteins from the mitochondrial intermembrane space then empty into the cytosol to activate proteases that dismantle the cell. The arrangement of Bax and Bak in membrane-bound complexes, and how the complexes porate the membrane, is far from being understood. However, recent data indicate that they first form symmetric BH3:groove dimers which can be linked via an interface between the α6-helices to form high order oligomers. Here, we review how Bax and Bak change conformation and oligomerize, as well as how oligomers might form a pore. This article is part of a Special Issue entitled Mitochondria: the deadly organelle.
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Sobko AA, Kovalchuk SI, Kotova EA, Antonenko YN. Induction of lipid flip-flop by colicin E1 — a hallmark of proteolipidic pore formation in liposome membranes. BIOCHEMISTRY (MOSCOW) 2010; 75:728-33. [DOI: 10.1134/s0006297910060076] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Majd S, Yusko EC, Billeh YN, Macrae MX, Yang J, Mayer M. Applications of biological pores in nanomedicine, sensing, and nanoelectronics. Curr Opin Biotechnol 2010; 21:439-76. [PMID: 20561776 PMCID: PMC3121537 DOI: 10.1016/j.copbio.2010.05.002] [Citation(s) in RCA: 264] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2010] [Revised: 05/03/2010] [Accepted: 05/06/2010] [Indexed: 12/29/2022]
Abstract
Biological protein pores and pore-forming peptides can generate a pathway for the flux of ions and other charged or polar molecules across cellular membranes. In nature, these nanopores have diverse and essential functions that range from maintaining cell homeostasis and participating in cell signaling to activating or killing cells. The combination of the nanoscale dimensions and sophisticated - often regulated - functionality of these biological pores make them particularly attractive for the growing field of nanobiotechnology. Applications range from single-molecule sensing to drug delivery and targeted killing of malignant cells. Potential future applications may include the use of nanopores for single strand DNA sequencing and for generating bio-inspired, and possibly, biocompatible visual detection systems and batteries. This article reviews the current state of applications of pore-forming peptides and proteins in nanomedicine, sensing, and nanoelectronics.
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Affiliation(s)
- Sheereen Majd
- Department of Biomedical Engineering, University of Michigan, 1101 Beal Avenue, Ann Arbor, Michigan 48109-2110, USA
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García-Sáez AJ, Fuertes G, Suckale J, Salgado J. Permeabilization of the Outer Mitochondrial Membrane by Bcl-2 Proteins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 677:91-105. [DOI: 10.1007/978-1-4419-6327-7_8] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Role of membrane lipids for the activity of pore forming peptides and proteins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 677:31-55. [PMID: 20687479 DOI: 10.1007/978-1-4419-6327-7_4] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Bilayer lipids, far from being passive elements, have multiple roles in polypeptide-dependent pore formation. Lipids participate at all stages of the formation of pores by providing the binding site for proteins and peptides, conditioning their active structure and modulating the molecular reorganization of the membrane complex. Such general functions of lipids superimpose to other particular roles, from electrostatic and curvature effects to more specific actions in cases like cholesterol, sphingolipids or cardiolipin. Pores are natural phenomena in lipid membranes. Driven by membrane fluctuations and packing defects, transient water pores are related to spontaneous lipid flip-flop and non-assisted ion permeation. In the absence ofproteins or peptides, these are rare short living events, with properties dependent on the lipid composition of the membrane. Their frequency increases under conditions of internal membrane disturbance of the lipid packing, like in the presence of membrane-bound proteins or peptides. These latter molecules, in fact, form dynamic supramolecular assemblies together with the lipids and transmembrane pores are one of the possible structures of the complex. Active peptides and proteins can thus be considered inducers or enhancers of pores which increase their probability and lifetime by modifying the thermodynamic membrane balance. This includes destabilizing the membrane lamellar structure, lowering the activation energy for pore formation and stabilizing the open pore structure.
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Sobko AA, Rokitskaya TI, Kotova EA. Histidine 440 controls the opening of colicin E1 channels in a lipid-dependent manner. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:1962-6. [DOI: 10.1016/j.bbamem.2009.06.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Revised: 06/05/2009] [Accepted: 06/19/2009] [Indexed: 11/17/2022]
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Peptide-lipid huge toroidal pore, a new antimicrobial mechanism mediated by a lactococcal bacteriocin, lacticin Q. Antimicrob Agents Chemother 2009; 53:3211-7. [PMID: 19470516 DOI: 10.1128/aac.00209-09] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Lacticin Q is a pore-forming bacteriocin produced by Lactococcus lactis QU 5, and its antimicrobial activity is in the nanomolar range. Lacticin Q induced calcein leakage from negatively charged liposomes. However, no morphological changes in the liposomes were observed by light scattering. Concomitantly with the calcein leakage, lacticin Q was found to translocate from the outer to the inner leaflet of the liposomes, after it initially bound to the membrane within 2 s. Lacticin Q also induced lipid flip-flop. These results reveal that the antimicrobial mechanism of lacticin Q can be described by the toroidal pore model. This is the first report of a bacteriocin of gram-positive bacteria that forms a toroidal pore. From liposomes, lacticin Q leaked fluorescence-labeled dextran with a diameter of 4.6 nm. In addition, lacticin Q caused the leakage of small proteins, such as the green fluorescent protein, from live bacterial cells. There are no other reports of antimicrobial peptides that exhibit protein leakage properties. The proposed pore formation model of lacticin Q is as follows: (i) quick binding to outer membrane leaflets; (ii) the formation of at least 4.6-nm pores, causing protein leakage with lipid flip-flop; and (iii) the migration of lacticin Q molecules from the outer to the inner membrane leaflets. Consequently, we termed the novel pore model in the antimicrobial mechanism of lacticin Q a "huge toroidal pore."
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44
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Kienker PK, Jakes KS, Finkelstein A. Identification of channel-lining amino acid residues in the hydrophobic segment of colicin Ia. ACTA ACUST UNITED AC 2009; 132:693-707. [PMID: 19029376 PMCID: PMC2585860 DOI: 10.1085/jgp.200810042] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Colicin Ia is a bactericidal protein of 626 amino acid residues that kills its target cell by forming a channel in the inner membrane; it can also form voltage-dependent channels in planar lipid bilayer membranes. The channel-forming activity resides in the carboxy-terminal domain of ∼177 residues. In the crystal structure of the water-soluble conformation, this domain consists of a bundle of 10 α-helices, with eight mostly amphipathic helices surrounding a hydrophobic helical hairpin (helices H8-H9). We wish to know how this structure changes to form a channel in a lipid bilayer. Although there is evidence that the open channel has four transmembrane segments (H8, H9, and parts of H1 and H6-H7), their arrangement relative to the pore is largely unknown. Given the lack of a detailed structural model, it is imperative to better characterize the channel-lining protein segments. Here, we focus on a segment of 44 residues (573–616), which in the crystal structure comprises the H8-H9 hairpin and flanking regions. We mutated each of these residues to a unique cysteine, added the mutant colicins to the cis side of planar bilayers to form channels, and determined whether sulfhydryl-specific methanethiosulfonate reagents could alter the conduction of ions through the open channel. We found a pattern of reactivity consistent with parts of H8 and H9 lining the channel as α-helices, albeit rather short ones for spanning a lipid bilayer (12 residues). The effects of the reactions on channel conductance and selectivity tend to be greater for residues near the amino terminus of H8 and the carboxy terminus of H9, with particularly large effects for G577C, T581C, and G609C, suggesting that these residues may occupy a relatively constricted region near the cis end of the channel.
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Affiliation(s)
- Paul K Kienker
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
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45
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Ho D, Merrill AR. Evidence for the Amphipathic Nature and Tilted Topology of Helices 4 and 5 in the Closed State of the Colicin E1 Channel. Biochemistry 2009; 48:1369-80. [DOI: 10.1021/bi801906v] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Derek Ho
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - A. Rod Merrill
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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46
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Andreeva-Kovalevskaya ZI, Solonin AS, Sineva EV, Ternovsky VI. Pore-forming proteins and adaptation of living organisms to environmental conditions. BIOCHEMISTRY (MOSCOW) 2009; 73:1473-92. [DOI: 10.1134/s0006297908130087] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Baboolal TG, Conroy MJ, Gill K, Ridley H, Visudtiphole V, Bullough PA, Lakey JH. Colicin N binds to the periphery of its receptor and translocator, outer membrane protein F. Structure 2008; 16:371-9. [PMID: 18334212 PMCID: PMC2581486 DOI: 10.1016/j.str.2007.12.023] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2007] [Revised: 12/20/2007] [Accepted: 12/21/2007] [Indexed: 11/24/2022]
Abstract
Colicins kill Escherichia coli after translocation across the outer membrane. Colicin N displays an unusually simple translocation pathway, using the outer membrane protein F (OmpF) as both receptor and translocator. Studies of this binary complex may therefore reveal a significant component of the translocation pathway. Here we show that, in 2D crystals, colicin is found outside the porin trimer, suggesting that translocation may occur at the protein-lipid interface. The major lipid of the outer leaflet interface is lipopolysaccharide (LPS). It is further shown that colicin N binding displaces OmpF-bound LPS. The N-terminal helix of the pore-forming domain, which is not required for pore formation, rearranges and binds to OmpF. Colicin N also binds artificial OmpF dimers, indicating that trimeric symmetry plays no part in the interaction. The data indicate that colicin is closely associated with the OmpF-lipid interface, providing evidence that this peripheral pathway may play a role in colicin transmembrane transport.
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Affiliation(s)
- Thomas G Baboolal
- The Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle-upon-Tyne, NE2 4HH, United Kingdom
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Dubovskii PV, Volynsky PE, Polyansky AA, Karpunin DV, Chupin VV, Efremov RG, Arseniev AS. Three-dimensional structure/hydrophobicity of latarcins specifies their mode of membrane activity. Biochemistry 2008; 47:3525-33. [PMID: 18293934 DOI: 10.1021/bi702203w] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Latarcins, linear peptides from the Lachesana tarabaevi spider venom, exhibit a broad-spectrum antimicrobial activity, likely acting on the bacterial cytoplasmic membrane. We study their spatial structures and interaction with model membranes by a combination of experimental and theoretical methods to reveal the structure-activity relationship. In this work, a 26 amino acid peptide, Ltc1, was investigated. Its spatial structure in detergent micelles was determined by (1)H nuclear magnetic resonance (NMR) and refined by Monte Carlo simulations in an implicit water-octanol slab. The Ltc1 molecule was found to form a straight uninterrupted amphiphilic helix comprising 8-23 residues. A dye-leakage fluorescent assay and (31)P NMR spectroscopy established that the peptide does not induce the release of fluorescent marker nor deteriorate the bilayer structure of the membranes. The voltage-clamp technique showed that Ltc1 induces the current fluctuations through planar membranes when the sign of the applied potential coincides with the one across the bacterial inner membrane. This implies that Ltc1 acts on the membranes via a specific mechanism, which is different from the carpet mode demonstrated by another latarcin, Ltc2a, featuring a helix-hinge-helix structure with a hydrophobicity gradient along the peptide chain. In contrast, the hydrophobic surface of the Ltc1 helix is narrow-shaped and extends with no gradient along the axis. We have also disclosed a number of peptides, structurally homologous to Ltc1 and exhibiting similar membrane activity. This indicates that the hydrophobic pattern of the Ltc1 helix and related antimicrobial peptides specifies their activity mechanism. The latter assumes the formation of variable-sized lesions, which depend upon the potential across the membrane.
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Affiliation(s)
- Peter V Dubovskii
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, 16/10 Miklukho-Maklaya Str., Moscow 117997, Russia.
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Zakharov SD, Hulleman JD, Dutseva EA, Antonenko YN, Rochet JC, Cramer WA. Helical α-Synuclein Forms Highly Conductive Ion Channels. Biochemistry 2007; 46:14369-79. [DOI: 10.1021/bi701275p] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Stanislav D. Zakharov
- Departments of Biological Sciences and Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907-2054, Institute of Basic Biological Problems, Russian Academy of Sciences, Puschino, Moscow Region 140290, Russian Federation, and A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russian Federation
| | - John D. Hulleman
- Departments of Biological Sciences and Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907-2054, Institute of Basic Biological Problems, Russian Academy of Sciences, Puschino, Moscow Region 140290, Russian Federation, and A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russian Federation
| | - Elena A. Dutseva
- Departments of Biological Sciences and Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907-2054, Institute of Basic Biological Problems, Russian Academy of Sciences, Puschino, Moscow Region 140290, Russian Federation, and A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russian Federation
| | - Yuri N. Antonenko
- Departments of Biological Sciences and Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907-2054, Institute of Basic Biological Problems, Russian Academy of Sciences, Puschino, Moscow Region 140290, Russian Federation, and A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russian Federation
| | - Jean-Christophe Rochet
- Departments of Biological Sciences and Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907-2054, Institute of Basic Biological Problems, Russian Academy of Sciences, Puschino, Moscow Region 140290, Russian Federation, and A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russian Federation
| | - William A. Cramer
- Departments of Biological Sciences and Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, Indiana 47907-2054, Institute of Basic Biological Problems, Russian Academy of Sciences, Puschino, Moscow Region 140290, Russian Federation, and A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russian Federation
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Madan V, Sánchez-Martínez S, Vedovato N, Rispoli G, Carrasco L, Nieva JL. Plasma membrane-porating domain in poliovirus 2B protein. A short peptide mimics viroporin activity. J Mol Biol 2007; 374:951-64. [PMID: 17963782 DOI: 10.1016/j.jmb.2007.09.058] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2007] [Revised: 09/13/2007] [Accepted: 09/20/2007] [Indexed: 11/30/2022]
Abstract
Picornavirus 2B, a non-structural protein required for effective viral replication, has been implicated in cell membrane permeabilization during the late phases of infection. Here, we have approached the molecular mechanism of this process by assessing the pore-forming activity of an overlapping peptide library that spanned the complete 2B sequence. At non-cytopathic concentrations, only the P3 peptide, spanning 2B residues 35-55, effectively assembled hydrophilic pores that allowed diffusion of low molecular mass solutes across the cell plasma membrane (IC(50) approximately 4x10(-7) M) and boundary liposome bilayers (starting at peptide to lipid molar ratios>1:10(4)). Circular dichroism data were consistent with its capacity to fold as a helix in a membrane-like environment. Furthermore, addition of this peptide to a sealed plasma-membrane model, consisting of retinal rod outer segments patch-clamped in a whole-cell configuration, induced ion channel activity within seconds at concentrations as low as 10(-8) M. Thus, we have established a "one-helix" 2B version that possesses the intrinsic pore-forming activity required to directly and effectively permeabilize the cell plasma membrane. We conclude that 2B viroporin can be classified as a genuine pore-forming toxin of viral origin, which is produced intracellularly at certain times post infection.
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Affiliation(s)
- Vanesa Madan
- Centro de Biología Molecular (CSIC-UAM), Universidad Autónoma de Madrid, Canto Blanco, 28049 Madrid, Spain
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