1
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Haro-Reyes T, Ortega-Blake I. Notable enhancement of Amphotericin B channel activity by applied pressures in the range of MS channel activation. Biochim Biophys Acta Biomembr 2024; 1866:184326. [PMID: 38703804 DOI: 10.1016/j.bbamem.2024.184326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 04/12/2024] [Accepted: 04/23/2024] [Indexed: 05/06/2024]
Abstract
The mechanism of Amphotericin B at the membrane is still subject of debate, with the prevailing hypothesis being the formation of pores. The activity of these pores is influenced by various factors. Recently aggregation in solution and insertion in the membrane had been highlighted as crucial for action of the drug Here we investigated the effect of applied pressure on the activity of Amphotericin B. Our findings demonstrate that applied pressure of 50 mmHg is sufficient to enhance the activity. We interpreted the results as supporting the idea that pressure fractures the membrane and promotes the insertion of the polyene.
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Affiliation(s)
- Tammy Haro-Reyes
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Av. Universidad s/n, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico
| | - Iván Ortega-Blake
- Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Av. Universidad s/n, Col. Chamilpa, Cuernavaca, Morelos 62210, Mexico.
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2
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Duart G, Graña-Montes R, Pastor-Cantizano N, Mingarro I. Experimental and computational approaches for membrane protein insertion and topology determination. Methods 2024:S1046-2023(24)00088-4. [PMID: 38604415 DOI: 10.1016/j.ymeth.2024.03.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 03/13/2024] [Accepted: 03/22/2024] [Indexed: 04/13/2024] Open
Abstract
Membrane proteins play pivotal roles in a wide array of cellular processes and constitute approximately a quarter of the protein-coding genes across all organisms. Despite their ubiquity and biological significance, our understanding of these proteins remains notably less comprehensive compared to their soluble counterparts. This disparity in knowledge can be attributed, in part, to the inherent challenges associated with employing specialized techniques for the investigation of membrane protein insertion and topology. This review will center on a discussion of molecular biology methodologies and computational prediction tools designed to elucidate the insertion and topology of helical membrane proteins.
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Affiliation(s)
- Gerard Duart
- Departament de Bioquímica i Biologia Molecular, Institut Universitari de Biotecnologia i Biomedicina (BIOTECMED), Universitat de València, E-46100 Burjassot, Spain
| | - Ricardo Graña-Montes
- Departament de Bioquímica i Biologia Molecular, Institut Universitari de Biotecnologia i Biomedicina (BIOTECMED), Universitat de València, E-46100 Burjassot, Spain
| | - Noelia Pastor-Cantizano
- Departament de Bioquímica i Biologia Molecular, Institut Universitari de Biotecnologia i Biomedicina (BIOTECMED), Universitat de València, E-46100 Burjassot, Spain
| | - Ismael Mingarro
- Departament de Bioquímica i Biologia Molecular, Institut Universitari de Biotecnologia i Biomedicina (BIOTECMED), Universitat de València, E-46100 Burjassot, Spain.
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3
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Khurana H, Pucadyil TJ. "Gearing" up for dynamin-catalyzed membrane fission. Curr Opin Cell Biol 2023; 83:102204. [PMID: 37451176 DOI: 10.1016/j.ceb.2023.102204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 06/13/2023] [Accepted: 06/16/2023] [Indexed: 07/18/2023]
Abstract
Endocytic dynamins self-assemble into helical scaffolds and utilize energy from GTP hydrolysis to constrict and sever tubular membranous necks of budded endocytic intermediates. They bind the membrane using a pleckstrin-homology domain (PHD). The PHD is characterized by four unstructured loops, two of which partially insert into the membrane. Recent studies reveal that loop insertion lowers the bending rigidity of the membrane and that mutations in these two loops produce separable and opposite effects on the efficiency of dynamin-catalyzed membrane fission. Here, we review the current understanding of dynamin-catalyzed membrane fission and attempt to reconcile contrasting notions that have emerged from biochemical and cellular studies evaluating the role of the PHD in this process. We propose that two membrane-inserting loops act as "gears" that define the catalytic efficiency of the dynamin helical scaffold in membrane fission.
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Affiliation(s)
- Himani Khurana
- Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune 411008, Maharashtra, India
| | - Thomas J Pucadyil
- Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune 411008, Maharashtra, India.
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4
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Dalbey RE, Kaushik S, Kuhn A. YidC as a potential antibiotic target. Biochim Biophys Acta Mol Cell Res 2023; 1870:119403. [PMID: 36427551 DOI: 10.1016/j.bbamcr.2022.119403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 11/16/2022] [Accepted: 11/18/2022] [Indexed: 11/24/2022]
Abstract
The membrane insertase YidC, is an essential bacterial component and functions in the folding and insertion of many membrane proteins during their biogenesis. It is a multispanning protein in the inner (cytoplasmic) membrane of Escherichia coli that binds its substrates in the "greasy slide" through hydrophobic interaction. The hydrophilic part of the substrate transiently localizes in the groove of YidC before it is translocated into the periplasm. The groove, which is flanked by the greasy slide, is within the center of the membrane, and provides a promising target for inhibitors that would block the insertase function of YidC. In addition, since the greasy slide is available for the binding of various substrates, it could also provide a binding site for inhibitory molecules. In this review we discuss in detail the structure and the mechanism of how YidC interacts not only with its substrates, but also with its partner proteins, the SecYEG translocase and the SRP signal recognition particle. Insight into the substrate binding to the YidC catalytic groove is presented. We wind up the review with the idea that the hydrophilic groove would be a potential site for drug binding and the feasibility of YidC-targeted drug development.
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Affiliation(s)
- Ross E Dalbey
- Dept. of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, United States of America.
| | - Sharbani Kaushik
- Dept. of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, United States of America
| | - Andreas Kuhn
- Institute of Biology, University of Hohenheim, Stuttgart 70599, Germany.
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5
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Jung SJ, Yun M, Yim C, Hong S, Huh WK, Kim H. Expression level of Sec62 modulates membrane insertion of marginally hydrophobic segments. Biochim Biophys Acta Biomembr 2022; 1864:184051. [PMID: 36122759 DOI: 10.1016/j.bbamem.2022.184051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2022] [Revised: 08/08/2022] [Accepted: 09/09/2022] [Indexed: 06/15/2023]
Abstract
In the endoplasmic reticulum (ER) membrane, transmembrane (TM) domain insertion occurs through the Sec61 channel with its auxiliary components, including Sec62. Sec62 interacts with the Sec61 channel and is located on the front side of the Sec61 lateral gate, an entry site for TM domains to the lipid bilayer. Overexpression of Sec62 led to a growth defect in yeast, and we investigated its effects on protein translocation and membrane insertion by pulse labeling of Sec62 client proteins. Our data show that the insertion efficiency of marginally hydrophobic TM segments is reduced upon Sec62 overexpression. This result suggests a potential regulatory role of Sec62 as a gatekeeper of the lateral gate, thereby modulating the insertion threshold of TM segments.
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Affiliation(s)
- Sung-Jun Jung
- School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 08826, South Korea
| | - Mekang Yun
- School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 08826, South Korea
| | - Chewon Yim
- School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 08826, South Korea
| | - Sujin Hong
- School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 08826, South Korea
| | - Won-Ki Huh
- School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 08826, South Korea
| | - Hyun Kim
- School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul 08826, South Korea.
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6
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Varela L, Hendry AC, Cassar J, Martin-Escolano R, Cantoni D, Ossa F, Edwards JC, Abdul-Salam V, Ortega-Roldan JL. Zn2+ triggered two-step mechanism of CLIC1 membrane insertion and activation into chloride channels. J Cell Sci 2022; 135:276009. [PMID: 35833483 PMCID: PMC9511705 DOI: 10.1242/jcs.259704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Accepted: 07/04/2022] [Indexed: 11/21/2022] Open
Abstract
The chloride intracellular channel (CLIC) protein family displays the unique feature of altering its structure from a soluble form to a membrane-bound chloride channel. CLIC1, a member of this family, is found in the cytoplasm or in internal and plasma membranes, with membrane relocalisation linked to endothelial disfunction, tumour proliferation and metastasis. The molecular switch promoting CLIC1 activation remains under investigation. Here, cellular Cl− efflux assays and immunofluorescence microscopy studies have identified intracellular Zn2+ release as the trigger for CLIC1 activation and membrane insertion. Biophysical assays confirmed specific binding to Zn2+, inducing membrane association and enhancing Cl− efflux in a pH-dependent manner. Together, our results identify a two-step mechanism with Zn2+ binding as the molecular switch promoting CLIC1 membrane insertion, followed by pH-mediated activation of Cl− efflux. Summary: Identification of a two-step mechanism of CLIC1 membrane insertion based on Zn2+ binding and pH activation of Cl− efflux.
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Affiliation(s)
- Lorena Varela
- School of Biosciences. University of Kent. CT2 7NJ. Canterbury, UK
| | - Alex C Hendry
- School of Biosciences. University of Kent. CT2 7NJ. Canterbury, UK
| | - Joseph Cassar
- School of Biosciences. University of Kent. CT2 7NJ. Canterbury, UK
| | | | - Diego Cantoni
- Medway School of Pharmacy, The Universities of Kent and Greenwich at Medway, Chatham, ME7 4TB, UK
| | - Felipe Ossa
- Centre for Cardiovascular Medicine and Device Innovation, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - John C Edwards
- Department of Internal Medicine, Saint Louis University, St. Louis, MO, USA
| | - Vahitha Abdul-Salam
- Centre for Cardiovascular Medicine and Device Innovation, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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7
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Ataka K, Drauschke J, Stulberg V, Koksch B, Heberle J. pH-induced insertion of pHLIP into a lipid bilayer: In-situ SEIRAS characterization of a folding intermediate at neutral pH. Biochim Biophys Acta Biomembr 2022; 1864:183873. [PMID: 35104491 DOI: 10.1016/j.bbamem.2022.183873] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 11/22/2021] [Accepted: 01/20/2022] [Indexed: 06/14/2023]
Abstract
The pH low insertion peptide (pHLIP) is a pH-sensitive cell penetrating peptide that transforms from an unstructured coil on the membrane surface at pH > 7, to a transmembrane (TM) α-helix at pH < 5. By exploiting this unique property, pHLIP attracts interest as a potential tool for drug delivery and visualisation of acidic tissues produced by various maladies such as cancer, inflammation, hypoxia etc. Even though the structures of initial and end states of pHLIP insertion have been widely accepted, the intermediate structures in between these two states are less clear. Here, we have applied in situ Surface-Enhanced Infrared Absorption spectroscopy to examine the pH-induced insertion and folding processes of pHLIP into a solid-supported lipid bilayer. We show that formation of partially helical structure already takes place at pH only slightly below 7.0, but with the helical axis parallel to the membrane surface. The peptide starts to reorientate its helix from horizontal to vertical direction, accompanied by the insertion into the TM region at pH < 6.2. Further insertion into the TM region of the peptide results in an increase of inherent α-helical structure and complete secondary structure formation at pH 5.3. Analysis of the changes of the carboxylate vibrational bands upon pH titration shows two distinctive groups of aspartates and glutamates with pKa values of 4.5 and 6.3, respectively. Comparison to the amide bands of the peptide backbone suggests that the latter Asp/Glu groups are directly involved in the conformational changes of pHLIP in the respective intermediate states.
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Affiliation(s)
- Kenichi Ataka
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
| | - Janina Drauschke
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Valentina Stulberg
- Institute for Chemistry and Biochemistry, Department of Biology, Chemistry, Pharmacy, Freie Universität Berlin, Arnimallee 20, 14195, Berlin, Germany
| | - Beate Koksch
- Institute for Chemistry and Biochemistry, Department of Biology, Chemistry, Pharmacy, Freie Universität Berlin, Arnimallee 20, 14195, Berlin, Germany
| | - Joachim Heberle
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
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8
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Waeytens J, Turbant F, Arluison V, Raussens V, Wien F. Analysis of Bacterial Amyloid Interaction with Lipidic Membrane by Orientated Circular Dichroism and Infrared Spectroscopies. Methods Mol Biol 2022; 2538:217-234. [PMID: 35951303 DOI: 10.1007/978-1-0716-2529-3_15] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD), and orientated circular dichroism (OCD) are complementary spectroscopies widely used for the analysis of protein samples such as the amyloids commonly renowned as neurodegenerative agents. Determining the secondary structure content of proteins, such as aggregated β-sheets inside the amyloids and in various environments, including membranes and lipids, has made these techniques very valuable and complemental to high-resolution techniques such as nuclear magnetic resonance (NMR), X-ray crystallography, and cryo-electron microscopy. FTIR and CD are extremely sensitive to structural changes of proteins due to environmental changes. Furthermore, FTIR provides information on lipid modifications upon protein binding, whereas synchrotron radiation CD (SRCD) and OCD are sensitive to the subtle structural changes occurring in β-sheet-rich proteins and their orientation or alignment with lipid bilayers. FTIR and CD techniques allow the identification of parallel and antiparallel β-sheet content and are therefore complementary. In this chapter, we present FTIR and CD/OCD applications to study the interactions of bacterial amyloids with membranes and lipids. Moreover, we show how to decipher the spectroscopic signals to obtain information on the molecular structure of amyloids and their interaction with lipids, addressing potential amyloid insertion into membranes and the lipid bilayer adjustments observed.
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Affiliation(s)
- Jehan Waeytens
- Centre de Biologie structurale et de Bioinformatique, Structure et Fonction des Membranes Biologiques, Université libre de Bruxelles, Bruxelles, Belgium
- Institut de Chimie Physique, CNRS UMR8000, Université Paris-Sud, Université Paris-Saclay, Orsay, France
| | - Florian Turbant
- Laboratoire Léon Brillouin LLB, CEA, CNRS UMR12, Université Paris Saclay, Gif-sur-Yvette, France
| | - Véronique Arluison
- Laboratoire Léon Brillouin LLB, CEA, CNRS UMR12, Université Paris Saclay, Gif-sur-Yvette, France
- Université de Paris Cité, Paris, France
| | - Vincent Raussens
- Centre de Biologie structurale et de Bioinformatique, Structure et Fonction des Membranes Biologiques, Université libre de Bruxelles, Bruxelles, Belgium.
| | - Frank Wien
- Synchrotron SOLEIL, L'Orme des Merisiers, Gif-sur-Yvette, France.
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9
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Amaral JL, Souza PFN, Oliveira JTA, Freire VN, Sousa DOB. Computational approach, scanning electron and fluorescence microscopies revealed insights into the action mechanisms of anticandidal peptide Mo-CBP 3-PepIII. Life Sci 2021; 281:119775. [PMID: 34186044 DOI: 10.1016/j.lfs.2021.119775] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 06/09/2021] [Accepted: 06/20/2021] [Indexed: 11/17/2022]
Abstract
AIMS The Candida genus is composed of opportunistic pathogens that threaten public health. Given the increase in resistance to current drugs, it is necessary to develop new drugs to treat infections by these pathogens. Antimicrobial peptides are promising alternative molecules with low cost, broad action spectrum and low resistance induction. This study aimed to clarify the action mechanisms of synthetic peptides against Candida albicans. MAIN METHODS The mode of action of the anticandidal peptides Mo-CBP3-PepIII were analyzed through molecular dynamics and quantum biochemistry methods against Exo-β-1,3-glucanase (EXG), vital to cell wall metabolism. Furthermore, scanning electron (SEM) and fluorescence (FM) microscopies were employed to corroborate the in silico data. KEY FINDINGS Mo-CBP3-PepIII strongly interacted with EXG (-122.2 kcal mol-1) at the active site, higher than the commercial inhibitor pepstatin. Also, molecular dynamics revealed the insertion of Mo-CBP3-PepIII into the yeast membrane. SEM analyses revealed that Mo-CBP3-PepIII induced cracks and scars of the cell wall and FM analyses confirmed the pore formation on the Candida membrane. SIGNIFICANCE Mo-CBP3-PepIII has strong potential as a new drug with a broad spectrum of action, given its different mode of action compared to conventional drugs.
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Affiliation(s)
- Jackson L Amaral
- Department of Biochemistry and Molecular Biology, Federal University of Ceará, Fortaleza, Ceará CEP 60.440-554, Brazil; Department of Physics, Federal University of Ceará, Fortaleza, Ceará CEP 60.440-554, Brazil.
| | - Pedro F N Souza
- Department of Biochemistry and Molecular Biology, Federal University of Ceará, Fortaleza, Ceará CEP 60.440-554, Brazil
| | - Jose T A Oliveira
- Department of Biochemistry and Molecular Biology, Federal University of Ceará, Fortaleza, Ceará CEP 60.440-554, Brazil
| | - Valder N Freire
- Department of Physics, Federal University of Ceará, Fortaleza, Ceará CEP 60.440-554, Brazil
| | - Daniele O B Sousa
- Department of Biochemistry and Molecular Biology, Federal University of Ceará, Fortaleza, Ceará CEP 60.440-554, Brazil.
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10
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Sun S, Tang X, Guo Y, Hu J. Endoplasmic reticulum composition and form: Proteins in and out. Curr Opin Cell Biol 2021; 71:1-6. [PMID: 33611096 DOI: 10.1016/j.ceb.2021.01.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 01/18/2021] [Accepted: 01/19/2021] [Indexed: 02/07/2023]
Abstract
The endoplasmic reticulum (ER) is the main harbor for newly synthesized proteins in eukaryotic cells. Through a continuous membrane network of sheets and tubules, the ER hosts secretory proteins, integral membrane proteins, and luminal proteins of the endomembrane system. These proteins are translated by ribosomes outside the ER and require subsequent integration into or translocation across the lipid bilayer of the ER. They are then modified post-translationally and folded in the ER. Some of these proteins are packaged into coat protein complex II-coated vesicles for export. Here, we review recent advances in understanding the mechanism of protein translocation and transmembrane domain insertion in the ER, summarize new insights into selective cargo packaging, and discuss the roles of ER morphological dynamics in these processes.
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11
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Abstract
Phosphoinositides play important roles in the regulation of protein recruitment at specialized membrane domains, protein activity, and membrane dynamics. Phosphoinositide-protein interplay occurs via multiple mechanisms and proteins associate with membranes through different binding patterns. Determinations of membrane-binding mode and membrane penetration depth of proteins in lipid bilayer are thus important steps in characterizing the molecular mechanisms of membrane-protein interactions. Here, we show two standard in vitro assays using liposomes, diphenylhexatriene (DPH) anisotropy, and fluorescence quenching by brominated lipids to determine membrane penetration of proteins into lipid bilayer. These methods will provide useful tools to study membrane-protein association and uncover molecular details of protein-lipid interplay, which are important for understanding biological functions of membrane-associated proteins and membrane dynamics.
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12
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Pettersson P, Patrick J, Jakob M, Jacobs M, Klösgen RB, Wennmalm S, Mäler L. Soluble TatA forms oligomers that interact with membranes: Structure and insertion studies of a versatile protein transporter. Biochim Biophys Acta Biomembr 2020; 1863:183529. [PMID: 33279512 DOI: 10.1016/j.bbamem.2020.183529] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 11/25/2020] [Accepted: 11/30/2020] [Indexed: 01/24/2023]
Abstract
The twin-arginine translocase (Tat) mediates the transport of already-folded proteins across membranes in bacteria, plants and archaea. TatA is a small, dynamic subunit of the Tat-system that is believed to be the active component during target protein translocation. TatA is foremost characterized as a bitopic membrane protein, but has also been found to partition into a soluble, oligomeric structure of yet unknown function. To elucidate the interplay between the membrane-bound and soluble forms we have investigated the oligomers formed by Arabidopsis thaliana TatA. We used several biophysical techniques to study the oligomeric structure in solution, the conversion that takes place upon interaction with membrane models of different compositions, and the effect on bilayer integrity upon insertion. Our results demonstrate that in solution TatA oligomerizes into large objects with a high degree of ordered structure. Upon interaction with lipids, conformational changes take place and TatA disintegrates into lower order oligomers. The insertion of TatA into lipid bilayers causes a temporary leakage of small molecules across the bilayer. The disruptive effect on the membrane is dependent on the liposome's negative surface charge density, with more leakage observed for purely zwitterionic bilayers. Overall, our findings indicate that A. thaliana TatA forms oligomers in solution that insert into bilayers, a process that involves reorganization of the protein oligomer.
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Affiliation(s)
- Pontus Pettersson
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Joan Patrick
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Mario Jakob
- Institut für Biologie, Institutsbereich Pflanzenphysiologie, Martin-Luther University, DE-06120 Halle-Wittenberg, Germany
| | - Malte Jacobs
- Institut für Biologie, Institutsbereich Pflanzenphysiologie, Martin-Luther University, DE-06120 Halle-Wittenberg, Germany
| | - Ralf Bernd Klösgen
- Institut für Biologie, Institutsbereich Pflanzenphysiologie, Martin-Luther University, DE-06120 Halle-Wittenberg, Germany
| | - Stefan Wennmalm
- Department of Applied Physics, Biophysics Group, Science for Life Laboratory, Royal Institute of Technology, Solna SE-171 65, Sweden
| | - Lena Mäler
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden.
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13
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Ray S, Vazquez Reyes S, Xiao C, Sun J. Effects of membrane lipid composition on Mycobacterium tuberculosis EsxA membrane insertion: A dual play of fluidity and charge. Tuberculosis (Edinb) 2019; 118:101854. [PMID: 31430698 PMCID: PMC6817408 DOI: 10.1016/j.tube.2019.07.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 07/26/2019] [Accepted: 07/29/2019] [Indexed: 12/29/2022]
Abstract
As a key virulence factor of Mycobacterium tuberculosis, EsxA or 6-kDa early secreted antigenic target (ESAT-6) has been implicated in phagosome rupture and mycobacterial translocation from the phagosome to the cytosol within macrophages. Our previous studies have shown that EsxA permeabilizes liposomal membrane at acidic pH and a membrane-permeabilization defective mutant Q5K attenuates mycobacterial cytosolic translocation and virulence in macrophages. To further probe the mechanism of EsxA membrane permeabilization, here we characterized the effects of various lipid compositions, including biologically relevant phagosome-mimicking lipids and lipid rafts, on the structural stability and membrane insertion of EsxA WT and Q5K. We have found a complex dual play of membrane fluidity and charge in regulating EsxA membrane insertion. Moreover, Q5K affects the membrane insertion through a structure- and lipid composition-independent mechanism. The results of this study provide a novel insights into the mechanism of EsxA membrane interaction.
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Affiliation(s)
- Supriyo Ray
- Department of Chemistry, University of Texas at El Paso, 500 West University Avenue, El Paso, TX, 79968, USA.
| | - Salvador Vazquez Reyes
- Department of Biological Sciences, University of Texas at El Paso, 500 West University Avenue, TX, 79968, USA; Border Biomedical Research Center at University of Texas at El Paso, 500 West University Avenue, TX, 79968, USA
| | - Chuan Xiao
- Department of Chemistry, University of Texas at El Paso, 500 West University Avenue, El Paso, TX, 79968, USA; Border Biomedical Research Center at University of Texas at El Paso, 500 West University Avenue, TX, 79968, USA
| | - Jianjun Sun
- Department of Biological Sciences, University of Texas at El Paso, 500 West University Avenue, TX, 79968, USA; Border Biomedical Research Center at University of Texas at El Paso, 500 West University Avenue, TX, 79968, USA.
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14
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Hossain KR, Turkewitz DR, Holt SA, Herson L, Brown LJ, Cornell BA, Curmi PMG, Valenzuela SM. A conserved GXXXG motif in the transmembrane domain of CLIC proteins is essential for their cholesterol-dependant membrane interaction. Biochim Biophys Acta Gen Subj 2019; 1863:1243-1253. [PMID: 31075359 DOI: 10.1016/j.bbagen.2019.04.020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 04/25/2019] [Accepted: 04/29/2019] [Indexed: 12/21/2022]
Abstract
BACKGROUND Sterols have been reported to modulate conformation and hence the function of several membrane proteins. One such group is the Chloride Intracellular Ion Channel (CLIC) family of proteins. The CLIC protein family consists of six evolutionarily conserved protein members in vertebrates. These proteins exist as both monomeric soluble proteins and as membrane bound proteins. To date, the structure of their membrane-bound form remains unknown. In addition to several studies indicating cellular redox environment and pH as facilitators of CLIC1 insertion into membranes, we have also demonstrated that the spontaneous membrane insertion of CLIC1 is regulated by membrane cholesterol. METHOD We have performed Langmuir-film, Impedance Spectroscopy and Molecular Docking Simulations to study the role of this GXXXG motif in CLIC1 interaction with cholesterol. RESULTS Unlike CLIC1-wild-type protein, the G18A and G22A mutants, that form part of the GXXXG motif, showed much slower initial kinetics and lower ion channel activity compared to the native protein. This difference can be attributed to the significantly reduced membrane interaction and insertion rate of the mutant proteins and/or slower formation of the final membrane configuration of the mutant proteins once in the membrane. CONCLUSION In this study, our findings uncover the identification of a GXXXG motif in CLIC1, which likely serves as the cholesterol-binding domain, that facilitates the protein's membrane interaction and insertion. Furthermore, we were able to postulate a model by which CLIC1 can autonomously insert into membranes to form functional ion channels. GENERAL SIGNIFICANCE Members of the CLIC family of proteins demonstrate unusual structural and dual functional properties - as ion channels and enzymes. Elucidating how the CLIC proteins' interact with membranes, thus allowing them to switch between their soluble and membrane form, will provide key information as to a mechanism of moonlighting activity and a novel regulatory role for cholesterol in such a process.
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Affiliation(s)
- Khondker Rufaka Hossain
- School of Life Sciences, University of Technology Sydney, Sydney, New South Wales 2007, Australia
| | - Daniel R Turkewitz
- School of Life Sciences, University of Technology Sydney, Sydney, New South Wales 2007, Australia
| | - Stephen A Holt
- Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Height, Australian Centre for Neutron Scattering, New South Wales 2234, Australia
| | - Leonie Herson
- School of Life Sciences, University of Technology Sydney, Sydney, New South Wales 2007, Australia
| | - Louise J Brown
- Department of Molecular Sciences, Macquarie University, New South Wales 2109, Australia
| | - Bruce A Cornell
- Surgical Diagnostics Pty Ltd., Roseville, Sydney 2069, Australia; Institute for Biomedical Materials and Devices, University of Technology Sydney, Sydney, New South Wales 2007, Australia
| | - Paul M G Curmi
- School of Physics, The University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Stella M Valenzuela
- School of Life Sciences, University of Technology Sydney, Sydney, New South Wales 2007, Australia; Institute for Biomedical Materials and Devices, University of Technology Sydney, Sydney, New South Wales 2007, Australia.
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15
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Davis D, Suemitsu J, Wattenberg B. Transmembrane topology of mammalian ORMDL proteins in the endoplasmic reticulum as revealed by the substituted cysteine accessibility method (SCAM™). Biochim Biophys Acta Proteins Proteom 2019; 1867:382-95. [PMID: 30639427 DOI: 10.1016/j.bbapap.2019.01.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 12/19/2018] [Accepted: 01/06/2019] [Indexed: 01/05/2023]
Abstract
Sphingolipids are diverse lipids with essential, and occasionally opposing, functions in the cell and therefore tight control over biosynthesis is vital. Mechanisms governing this regulation are not understood. Initial steps in sphingolipid biosynthesis take place on the cytosolic face of the endoplasmic reticulum (ER). Serine palmitoyltransferase (SPT) is an ER-resident enzyme catalyzing the first-committed step in sphingolipid biosynthesis. Not surprisingly, SPT activity is tightly regulated. ORMDLs are ER-resident proteins recently identified as regulators of SPT activity. ORMDL proteins interact directly with SPT but the nature of this interaction is unknown. ORMDL protein sequences contain hydrophobic regions, yet algorithm-based predictions of transmembrane segments are highly ambiguous, making topology of this key regulator unclear. Here we report use of substituted cysteine accessibility to analyze topology of mammalian ORMDLs. We constructed multiple mutant ORMDLs, each containing a single cysteine strategically placed along the protein length. Combined use of selective membrane permeabilization with an impermeant cysteine modification reagent allowed us to assign transmembrane and cytosolic segments of ORMDL. We confirmed that mammalian ORMDL proteins transit the membrane four times, with amino- and carboxy termini facing the cytosol along with a large cytosolic loop. This model will allow us to determine details of the ORMDL-SPT interaction and identify regions acting as the "lipid sensor" to detect changes in cellular sphingolipid levels. We also observe that SPT and ORMDL are substantially resistant to extraction from membranes with non-ionic detergent, indirectly suggesting that both proteins reside in a specialized subdomain of the ER.
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16
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Abstract
The inner membrane of Gram-negative bacteria is a ~6 nm thick phospholipid bilayer. It forms a semi-permeable barrier between the cytoplasm and periplasm allowing only regulated export and import of ions, sugar polymers, DNA and proteins. Inner membrane proteins, embedded via hydrophobic transmembrane α-helices, play an essential role in this regulated trafficking: they mediate insertion into the membrane (insertases) or complete crossing of the membrane (translocases) or both. The Gram-negative inner membrane is equipped with a variety of different insertases and translocases. Many of them are specialized, taking care of the export of only a few protein substrates, while others have more general roles. Here, we focus on the three general export/insertion pathways, the secretory (Sec) pathway, YidC and the twin-arginine translocation (TAT) pathway, focusing closely on the Escherichia coli (E. coli) paradigm. We only briefly mention dedicated export pathways found in different Gram-negative bacteria. The Sec system deals with the majority of exported proteins and functions both as a translocase for secretory proteins and an insertase for membrane proteins. The insertase YidC assists the Sec system or operates independently on membrane protein clients. Sec and YidC, in common with most export pathways, require their protein clients to be in soluble non-folded states to fit through the translocation channels and grooves. The TAT pathway is an exception, as it translocates folded proteins, some loaded with prosthetic groups.
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Affiliation(s)
- Jozefien De Geyter
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven - University of Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Dries Smets
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven - University of Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Spyridoula Karamanou
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven - University of Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Anastassios Economou
- Laboratory of Molecular Bacteriology, Department of Microbiology and Immunology, Rega Institute for Medical Research, KU Leuven - University of Leuven, Herestraat 49, 3000, Leuven, Belgium.
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17
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Maity A, Sinha S, Ghosh Dastidar S. Dissecting the thermodynamic contributions of the charged residues in the membrane anchoring of Bcl-xl C-terminal domain. Chem Phys Lipids 2018; 218:112-124. [PMID: 30550879 DOI: 10.1016/j.chemphyslip.2018.12.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 11/20/2018] [Accepted: 12/09/2018] [Indexed: 11/28/2022]
Abstract
The C-terminal helix of the Bcl-xl is known to initiate the membrane insertion of the protein by anchoring into the mitochondrial outer membrane. The C-terminal charged residues of that helix, R232 and K233, are reported to have an important structural role in the process of that insertion. The present work provides a quantitative understanding of the thermodynamic contribution of these residues on the membrane insertion energy-profile, calculated from the Adaptive Biasing Force based MD simulations of 2.67 μs altogether. Interestingly, the effect of the single neutralizing mutations at the C-terminus, i.e. K233A or R232A, is easily tolerated by the peptide without impacting the nature of insertion energy-profile, indicating the efficiency of one positively charged residue to drive the insertion. Whereas a double mutant, i.e. R232A and K233A, makes a significant impact on the energy-profile by destabilizing the membrane-associated states, as well as the membrane-embedded states. The finding provides molecular-level mechanistic insight. The water-mediated interaction formed by the peptide polar side chains within the bilayer core is found to modulate the membrane response during peptide insertion and that subsequently regulates the insertion mechanism. Mutation of the C-terminal residues eventually alters such a cascade of interactions that results in an insertion through energetically more expensive pathway. Since any one of the positively charged residues at the terminal is critical to ensure the membrane insertion, it appears that the natural selection of 'two' instead of 'one' charged residue is redundant in the context of membrane anchoring but may be important for other biochemical events.
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Affiliation(s)
- Atanu Maity
- Division of Bioinformatics, Bose Institute, P-1/12 C.I.T. Scheme VII M, Kolkata, 700054, India
| | - Souvik Sinha
- Division of Bioinformatics, Bose Institute, P-1/12 C.I.T. Scheme VII M, Kolkata, 700054, India
| | - Shubhra Ghosh Dastidar
- Division of Bioinformatics, Bose Institute, P-1/12 C.I.T. Scheme VII M, Kolkata, 700054, India.
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18
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Lutfullahoğlu-Bal G, Keskin A, Seferoğlu AB, Dunn CD. Bacterial tail anchors can target to the mitochondrial outer membrane. Biol Direct 2017; 12:16. [PMID: 28738827 PMCID: PMC5525287 DOI: 10.1186/s13062-017-0187-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 07/10/2017] [Indexed: 01/15/2023] Open
Abstract
Background During the generation and evolution of the eukaryotic cell, a proteobacterial endosymbiont was re-fashioned into the mitochondrion, an organelle that appears to have been present in the ancestor of all present-day eukaryotes. Mitochondria harbor proteomes derived from coding information located both inside and outside the organelle, and the rate-limiting step toward the formation of eukaryotic cells may have been development of an import apparatus allowing protein entry to mitochondria. Currently, a widely conserved translocon allows proteins to pass from the cytosol into mitochondria, but how proteins encoded outside of mitochondria were first directed to these organelles at the dawn of eukaryogenesis is not clear. Because several proteins targeted by a carboxyl-terminal tail anchor (TA) appear to have the ability to insert spontaneously into the mitochondrial outer membrane (OM), it is possible that self-inserting, tail-anchored polypeptides obtained from bacteria might have formed the first gate allowing proteins to access mitochondria from the cytosol. Results Here, we tested whether bacterial TAs are capable of targeting to mitochondria. In a survey of proteins encoded by the proteobacterium Escherichia coli, predicted TA sequences were directed to specific subcellular locations within the yeast Saccharomyces cerevisiae. Importantly, TAs obtained from DUF883 family members ElaB and YqjD were abundantly localized to and inserted at the mitochondrial OM. Conclusions Our results support the notion that eukaryotic cells are able to utilize membrane-targeting signals present in bacterial proteins obtained by lateral gene transfer, and our findings make plausible a model in which mitochondrial protein translocation was first driven by tail-anchored proteins. Reviewers This article was reviewed by Michael Ryan and Thomas Simmen. Electronic supplementary material The online version of this article (doi:10.1186/s13062-017-0187-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | - Abdurrahman Keskin
- Department of Molecular Biology and Genetics, Koç University, 34450 Sarıyer, İstanbul, Turkey.,Present Address: Department of Biological Sciences, Columbia University, New York, NY, 10027, USA
| | - Ayşe Bengisu Seferoğlu
- Department of Molecular Biology and Genetics, Koç University, 34450 Sarıyer, İstanbul, Turkey
| | - Cory D Dunn
- Department of Molecular Biology and Genetics, Koç University, 34450 Sarıyer, İstanbul, Turkey. .,Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, P.O. Box 56, 00014, Helsinki, Finland.
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19
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Galassi VV, Arantes GM. Partition, orientation and mobility of ubiquinones in a lipid bilayer. Biochim Biophys Acta 2015; 1847:1560-73. [PMID: 26255075 DOI: 10.1016/j.bbabio.2015.08.001] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Revised: 07/02/2015] [Accepted: 08/04/2015] [Indexed: 01/11/2023]
Abstract
Ubiquinone is the universal mobile charge carrier involved in biological electron transfer processes. Its redox properties and biological function depend on the molecular partition and lateral diffusion over biological membranes. However, ubiquinone localization and dynamics within lipid bilayers are long debated and still uncertain. Here we present molecular dynamics simulations of several ubiquinone homologs with variable isoprenoid tail lengths complexed to phosphatidylcholine bilayers. Initially, a new force-field parametrization for ubiquinone is derived from and compared to high level quantum chemical data. Free energy profiles for ubiquinone insertion in the lipid bilayer are obtained with the new force-field. The profiles allow for the determination of the equilibrium location of ubiquinone in the membrane as well as for the validation of the simulation model by direct comparison with experimental partition coefficients. A detailed analysis of structural properties and interactions shows that the ubiquinone polar head group is localized at the water-bilayer interface at the same depth of the lipid glycerol groups and oriented normal to the membrane plane. Both the localization and orientation of ubiquinone head groups do not change significantly when increasing the number of isoprenoid units. The isoprenoid tail is extended and packed with the lipid acyl chains. For ubiquinones with long tails, the terminal isoprenoid units have high flexibility. Calculated ubiquinone diffusion coefficients are similar to that found for the phosphatidylcholine lipid. These results may have further implications for the mechanisms of ubiquinone transport and binding to respiratory and photosynthetic protein complexes.
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20
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Deacon JC, Engelman DM, Barrera FN. Targeting acidity in diseased tissues: mechanism and applications of the membrane-inserting peptide, pHLIP. Arch Biochem Biophys 2014; 565:40-8. [PMID: 25444855 DOI: 10.1016/j.abb.2014.11.002] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Revised: 10/30/2014] [Accepted: 11/04/2014] [Indexed: 12/24/2022]
Abstract
pHLIPs are a family of soluble ∼36 amino acid peptides, which bind to membrane surfaces. If the environment is acidic, a pHLIP folds and inserts across the membrane to form a stable transmembrane helix, thus preferentially locating itself in acidic tissues. Since tumors and other disease tissues are acidic, pHLIPs' low-pH targeting behavior leads to applications as carriers for diagnostic and surgical imaging agents. The energy of membrane insertion can also be used to promote the insertion of modestly polar, normally cell-impermeable cargos across the cell membrane into the cytosol of targeted cells, leading to applications in tumor-targeted delivery of therapeutic molecules. We review the biochemical and biophysical basis of pHLIPs' unique properties, diagnostic and therapeutic applications, and the principles upon which translational applications are being developed.
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Affiliation(s)
- John C Deacon
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT 06520, USA
| | - Donald M Engelman
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT 06520, USA
| | - Francisco N Barrera
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996, USA.
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21
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Abstract
Thyroid hormones (TH) cross the plasma membrane with the help of transporter proteins. As charged amino acid derivatives, TH cannot simply diffuse across a lipid bilayer membrane, despite their notorious hydrophobicity. The identification of monocarboxylate transporter 8 (MCT8, SLC16A2) as a specific and very active TH transporter paved the way to the finding that mutations in the MCT8 gene cause a syndrome of psychomotor retardation in humans. The purpose of this review is to introduce the current model of transmembrane transport and highlight the diversity of TH transmembrane transporters. The interactions of TH with plasma transfer proteins, T3 receptors, and deiodinase are summarized. It is shown that proteins may bind TH owing to their hydrophobic character in hydrophobic cavities and/or by specific polar interaction with the phenolic hydroxyl, the aminopropionic acid moiety, and by weak polar interactions with the iodine atoms. These findings are compared with our understanding of how TH transporters interact with substrate. The presumed effects of mutations in MCT8 on protein folding and transport function are explained in light of the available homology model.
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Affiliation(s)
- Ulrich Schweizer
- Institut für Biochemie und Molekularbiologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
- *Prof. Dr. Ulrich Schweizer, Institut für Biochemie und Molekularbiologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 11, DE-53115 Bonn (Germany), E-Mail
| | - Jörg Johannes
- Institut für Experimentelle Endokrinologie, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Dorothea Bayer
- Institut für Biochemie und Molekularbiologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
| | - Doreen Braun
- Institut für Biochemie und Molekularbiologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
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22
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Lin X, Parthasarathy K, Surya W, Zhang T, Mu Y, Torres J. A conserved tetrameric interaction of cry toxin helix α3 suggests a functional role for toxin oligomerization. Biochim Biophys Acta 2014; 1838:1777-84. [PMID: 24657394 DOI: 10.1016/j.bbamem.2014.03.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Revised: 03/10/2014] [Accepted: 03/14/2014] [Indexed: 12/16/2022]
Abstract
Crystal (Cry) toxins are widely used for insect control, but their mechanism of toxicity is still uncertain. These toxins can form lytic pores in vitro, and water soluble tetrameric pre-pore intermediates have been reported. Even the precise oligomeric state of the toxin in membranes, trimeric or tetrameric, is still a debated issue. Based on previous reports, we have assumed that interactions between toxin monomers in solution are at least partly mediated by domain I, and we have analyzed in silico the homo-oligomerization tendencies of the domain I α-helices individually. Using many homologous sequences for each α-helix, our strategy allows selection of evolutionarily conserved interactions. These interactions appeared only in helices α3 and α5, but only α3 produced a suitably oriented or α-helical sample in lipid bilayers, forming homotetramers in C14-betaine, and allowing determination of its rotational orientation in lipid bilayers using site-specific infrared dichroism (SSID). The determined orientation in the tetrameric model is in agreement with only one of the evolutionarily conserved models. In addition mutation R99E, which was found to inhibit oligomerization experimentally, greatly destabilized the tetramer in molecular dynamic simulations. In this model, helix 3 is able to form inter-monomer interactions without significant rearrangements of domain I, which is compatible with the available crystal structure of Cry toxins in solution. The model presented here at least partially explains the reported tetrameric oligomerization of Cry toxins in solution and the inhibition of this oligomerization by a synthetic α3 peptide.
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Affiliation(s)
- Xin Lin
- School of Biological Sciences, Nanyang Technological University, 60, Nanyang Drive, 637551, Singapore
| | - Krupakar Parthasarathy
- School of Biological Sciences, Nanyang Technological University, 60, Nanyang Drive, 637551, Singapore
| | - Wahyu Surya
- School of Biological Sciences, Nanyang Technological University, 60, Nanyang Drive, 637551, Singapore
| | - Tong Zhang
- School of Biological Sciences, Nanyang Technological University, 60, Nanyang Drive, 637551, Singapore
| | - Yuguang Mu
- School of Biological Sciences, Nanyang Technological University, 60, Nanyang Drive, 637551, Singapore
| | - Jaume Torres
- School of Biological Sciences, Nanyang Technological University, 60, Nanyang Drive, 637551, Singapore.
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23
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Bhat V, Olenick MB, Schuchardt BJ, Mikles DC, Deegan BJ, McDonald CB, Seldeen KL, Kurouski D, Faridi MH, Shareef MM, Gupta V, Lednev IK, Farooq A. Heat-induced fibrillation of BclXL apoptotic repressor. Biophys Chem 2013; 179:12-25. [PMID: 23714425 DOI: 10.1016/j.bpc.2013.04.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Revised: 04/24/2013] [Accepted: 04/30/2013] [Indexed: 12/18/2022]
Abstract
The BclXL apoptotic repressor bears the propensity to associate into megadalton oligomers in solution, particularly under acidic pH. Herein, using various biophysical methods, we analyze the effect of temperature on the oligomerization of BclXL. Our data show that BclXL undergoes irreversible aggregation and assembles into highly-ordered rope-like homogeneous fibrils with length in the order of mm and a diameter in the μm-range under elevated temperatures. Remarkably, the formation of such fibrils correlates with the decay of a largely α-helical fold into a predominantly β-sheet architecture of BclXL in a manner akin to the formation of amyloid fibrils. Further interrogation reveals that while BclXL fibrils formed under elevated temperatures show no observable affinity toward BH3 ligands, they appear to be optimally primed for insertion into cardiolipin bicelles. This salient observation strongly argues that BclXL fibrils likely represent an on-pathway intermediate for insertion into mitochondrial outer membrane during the onset of apoptosis. Collectively, our study sheds light on the propensity of BclXL to form amyloid-like fibrils with important consequences on its mechanism of action in gauging the apoptotic fate of cells in health and disease.
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Affiliation(s)
- Vikas Bhat
- Department of Biochemistry & Molecular Biology, Leonard Miller School of Medicine, University of Miami, Miami, FL 33136, USA
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