1
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Malard F, Sizun C, Thureau A, Carlier L, Lescop E. Structural transitions in TCTP tumor protein upon binding to the anti-apoptotic protein family member Mcl-1. J Biol Chem 2023:104830. [PMID: 37201583 PMCID: PMC10333598 DOI: 10.1016/j.jbc.2023.104830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Revised: 05/09/2023] [Accepted: 05/11/2023] [Indexed: 05/20/2023] Open
Abstract
Translationally Controlled Tumor Protein (TCTP) serves as a pro-survival factor in tumor cells, inhibiting the mitochondrial apoptosis pathway by enhancing the function of anti-apoptotic Bcl-2 family members Mcl-1 and Bcl-xL. TCTP specifically binds to Bcl-xL, preventing Bax-dependent Bcl-xL-induced cytochrome c release, and it reduces Mcl-1 turnover by inhibiting its ubiquitination, thereby decreasing Mcl-1-mediated apoptosis. TCTP harbors a BH3-like motif that forms a β-strand buried in the globular domain of the protein. In contrast, the crystal structure of the TCTP BH3-like peptide in complex with the Bcl-2 family member Bcl-xL reveals an α-helical conformation for the BH3-like motif, suggesting significant structural changes upon complex formation. Employing biochemical and biophysical methods, including limited proteolysis, circular dichroism NMR, and SAXS, we describe the TCTP complex with the Bcl-2 homolog Mcl-1. Our findings demonstrate that full-length TCTP binds to the BH3 binding groove of Mcl-1 via its BH3-like motif, experiencing conformational exchange at the interface on a micro- to milli-second timescale. Concurrently, the TCTP globular domain becomes destabilized, transitioning into a molten-globule state. Furthermore, we establish that the non-canonical residue D16 within TCTP BH3-like motif reduces stability while enhancing the dynamics of the intermolecular interface. In conclusion, we detail the structural plasticity of TCTP and discuss its implications for partner interactions and future anticancer drug design strategies aimed at targeting TCTP complexes.
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Affiliation(s)
- Florian Malard
- Institut de Chimie des Substances Naturelles, CNRS UPR 2301, Université Paris-Saclay, LabEx LERMIT, 1 avenue de la Terrasse, 91190 Gif-sur-Yvette, France
| | - Christina Sizun
- Institut de Chimie des Substances Naturelles, CNRS UPR 2301, Université Paris-Saclay, LabEx LERMIT, 1 avenue de la Terrasse, 91190 Gif-sur-Yvette, France
| | | | - Ludovic Carlier
- Laboratoire Des Biomolécules, LBM, Sorbonne Université, Ecole Normale Supérieure, PSL University, CNRS, Paris, France
| | - Ewen Lescop
- Institut de Chimie des Substances Naturelles, CNRS UPR 2301, Université Paris-Saclay, LabEx LERMIT, 1 avenue de la Terrasse, 91190 Gif-sur-Yvette, France.
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2
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Gupta MN, Uversky VN. Pre-Molten, Wet, and Dry Molten Globules en Route to the Functional State of Proteins. Int J Mol Sci 2023; 24:ijms24032424. [PMID: 36768742 PMCID: PMC9916686 DOI: 10.3390/ijms24032424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 01/23/2023] [Accepted: 01/23/2023] [Indexed: 01/28/2023] Open
Abstract
Transitions between the unfolded and native states of the ordered globular proteins are accompanied by the accumulation of several intermediates, such as pre-molten globules, wet molten globules, and dry molten globules. Structurally equivalent conformations can serve as native functional states of intrinsically disordered proteins. This overview captures the characteristics and importance of these molten globules in both structured and intrinsically disordered proteins. It also discusses examples of engineered molten globules. The formation of these intermediates under conditions of macromolecular crowding and their interactions with nanomaterials are also reviewed.
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Affiliation(s)
- Munishwar Nath Gupta
- Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology, Hauz Khas, New Delhi 110016, India
| | - Vladimir N. Uversky
- Department of Molecular Medicine and USF Health Byrd Alzheimer’s Research Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA
- Correspondence: ; Tel.: +1-813-494-5816
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3
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Waseem R, Singh Yadav N, Khan T, Ahmad F, Naqui Kazim S, Hassan I, Prakash A, Islam A. Molecular Basis of Structural Stability of Irisin: A Combined Molecular Dynamics Simulation and In vitro Studies for Urea-induced Denaturation. J Mol Liq 2023. [DOI: 10.1016/j.molliq.2022.121120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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4
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Giglio ML, Ituarte S, Ibañez AE, Dreon MS, Prieto E, Fernández PE, Heras H. Novel Role for Animal Innate Immune Molecules: Enterotoxic Activity of a Snail Egg MACPF-Toxin. Front Immunol 2020; 11:428. [PMID: 32231667 PMCID: PMC7082926 DOI: 10.3389/fimmu.2020.00428] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Accepted: 02/25/2020] [Indexed: 01/22/2023] Open
Abstract
Gastropod Molluscs rely exclusively on the innate immune system to protect from pathogens, defending their embryos through maternally transferred effectors. In this regard, Pomacea snail eggs, in addition to immune defenses, have evolved the perivitellin-2 or PV2 combining two immune proteins into a neurotoxin: a lectin and a pore-forming protein from the Membrane Attack Complex/Perforin (MACPF) family. This binary structure resembles AB-toxins, a group of toxins otherwise restricted to bacteria and plants. Many of these are enterotoxins, leading us to explore this activity in PV2. Enterotoxins found in bacteria and plants act mainly as pore-forming toxins and toxic lectins, respectively. In animals, although both pore-forming proteins and lectins are ubiquitous, no enterotoxins have been reported. Considering that Pomacea snail eggs ingestion induce morpho-physiological changes in the intestinal mucosa of rodents and is cytotoxic to intestinal cells in culture, we seek for the factor causing these effects and identified PmPV2 from Pomacea maculata eggs. We characterized the enterotoxic activity of PmPV2 through in vitro and in vivo assays. We determined that it withstands the gastrointestinal environment and resisted a wide pH range and enzymatic proteolysis. After binding to Caco-2 cells it promoted changes in surface morphology and an increase in membrane roughness. It was also cytotoxic to both epithelial and immune cells from the digestive system of mammals. It induced enterocyte death by a lytic mechanism and disrupted enterocyte monolayers in a dose-dependent manner. Further, after oral administration to mice PmPV2 attached to enterocytes and induced large dose-dependent morphological changes on their small intestine mucosa, reducing the absorptive surface. Additionally, PmPV2 was detected in the Peyer's patches where it activated lymphoid follicles and triggered apoptosis. We also provide evidence that the toxin can traverse the intestinal barrier and induce oral adaptive immunity with evidence of circulating antibody response. As a whole, these results indicate that PmPV2 is a true enterotoxin, a role that has never been reported to lectins or perforin in animals. This extends by convergent evolution the presence of plant- and bacteria-like enterotoxins to animals, thus expanding the diversity of functions of MACPF proteins in nature.
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Affiliation(s)
- Matías L Giglio
- Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner" (INIBIOLP), CONICET, CCT-La Plata, Universidad Nacional de la Plata (UNLP), La Plata, Argentina
| | - Santiago Ituarte
- Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner" (INIBIOLP), CONICET, CCT-La Plata, Universidad Nacional de la Plata (UNLP), La Plata, Argentina
| | - Andrés E Ibañez
- División de Vertebrados, Facultad de Ciencias Naturales y Museo (FCNyM), Universidad Nacional de La Plata, La Plata, Argentina
| | - Marcos S Dreon
- Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner" (INIBIOLP), CONICET, CCT-La Plata, Universidad Nacional de la Plata (UNLP), La Plata, Argentina
- Cátedra de Bioquímica y Biología Molecular, Facultad de Ciencias Médicas, Universidad Nacional de la Plata (UNLP), La Plata, Argentina
| | - Eduardo Prieto
- Instituto de Investigaciones Físico-químicas Teóricas y Aplicadas (INIFTA), CONICET, CCT-La Plata, Universidad Nacional de La Plata, La Plata, Argentina
| | - Patricia E Fernández
- Facultad de Ciencias Veterinarias (FEV), Instituto de Patología B. Epstein, Cátedra de Patología General Veterinaria, Universidad Nacional de La Plata (UNLP), La Plata, Argentina
| | - Horacio Heras
- Instituto de Investigaciones Bioquímicas de La Plata "Prof. Dr. Rodolfo R. Brenner" (INIBIOLP), CONICET, CCT-La Plata, Universidad Nacional de la Plata (UNLP), La Plata, Argentina
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5
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Kumar R, Kumar R, Sharma D, Garg M, Kumar V, Agarwal MC. Macromolecular crowding-induced molten globule states of the alkali pH-denatured proteins. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2018; 1866:1102-1114. [DOI: 10.1016/j.bbapap.2018.08.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 07/07/2018] [Accepted: 08/30/2018] [Indexed: 11/26/2022]
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6
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The fluorination effect of fluoroamphiphiles in cytosolic protein delivery. Nat Commun 2018; 9:1377. [PMID: 29636457 PMCID: PMC5893556 DOI: 10.1038/s41467-018-03779-8] [Citation(s) in RCA: 199] [Impact Index Per Article: 33.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2017] [Accepted: 03/08/2018] [Indexed: 11/18/2022] Open
Abstract
Direct delivery of proteins into cells avoids many drawbacks of gene delivery, and thus has emerging applications in biotherapy. However, it remains a challenging task owing to limited charges and relatively large size of proteins. Here, we report an efficient protein delivery system via the co-assembly of fluoroamphiphiles and proteins into nanoparticles. Fluorous substituents on the amphiphiles play essential roles in the formation of uniform nanoparticles, avoiding protein denaturation, efficient endocytosis, and maintaining low cytotoxicity. Structure-activity relationship studies reveal that longer fluorous chain length and higher fluorination degree contribute to more efficient protein delivery, but excess fluorophilicity on the polymer leads to the pre-assembly of fluoroamphiphiles into stable vesicles, and thus failed protein encapsulation and cytosolic delivery. This study highlights the advantage of fluoroamphiphiles over other existing strategies for intracellular protein delivery. Proteins can serve as means of medical treatment, but their efficient delivery to cells is difficult. Here, the authors present a type of polymers, fluoroamphiphiles, acting as chemical chaperones that can facilitate the import of proteins into the inner compartment, i.e. cytosol, of cells.
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7
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Insight into the functional and structural transition of garlic phytocystatin induced by urea and guanidine hydrochloride: A comparative biophysical study. Int J Biol Macromol 2018; 106:20-29. [DOI: 10.1016/j.ijbiomac.2017.07.172] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 07/20/2017] [Accepted: 07/29/2017] [Indexed: 01/29/2023]
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8
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Bischofberger M, Iacovache I, Boss D, Naef F, van der Goot FG, Molina N. Revealing Assembly of a Pore-Forming Complex Using Single-Cell Kinetic Analysis and Modeling. Biophys J 2016; 110:1574-1581. [PMID: 27074682 PMCID: PMC4833779 DOI: 10.1016/j.bpj.2016.02.035] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 02/15/2016] [Accepted: 02/22/2016] [Indexed: 11/21/2022] Open
Abstract
Many biological processes depend on the sequential assembly of protein complexes. However, studying the kinetics of such processes by direct methods is often not feasible. As an important class of such protein complexes, pore-forming toxins start their journey as soluble monomeric proteins, and oligomerize into transmembrane complexes to eventually form pores in the target cell membrane. Here, we monitored pore formation kinetics for the well-characterized bacterial pore-forming toxin aerolysin in single cells in real time to determine the lag times leading to the formation of the first functional pores per cell. Probabilistic modeling of these lag times revealed that one slow and seven equally fast rate-limiting reactions best explain the overall pore formation kinetics. The model predicted that monomer activation is the rate-limiting step for the entire pore formation process. We hypothesized that this could be through release of a propeptide and indeed found that peptide removal abolished these steps. This study illustrates how stochasticity in the kinetics of a complex process can be exploited to identify rate-limiting mechanisms underlying multistep biomolecular assembly pathways.
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Affiliation(s)
- Mirko Bischofberger
- Global Health Institute, Faculty of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; The Institute of Bioengineering, Faculty of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Ioan Iacovache
- Global Health Institute, Faculty of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Daniel Boss
- The Brain Mind Institute, Faculty of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Felix Naef
- The Institute of Bioengineering, Faculty of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - F Gisou van der Goot
- Global Health Institute, Faculty of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
| | - Nacho Molina
- Center of Synthetic and Systems Biology, University of Edinburgh, Edinburgh, United Kingdom.
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9
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Houwman JA, André E, Westphal AH, van Berkel WJH, van Mierlo CPM. The Ribosome Restrains Molten Globule Formation in Stalled Nascent Flavodoxin. J Biol Chem 2016; 291:25911-25920. [PMID: 27784783 PMCID: PMC5207065 DOI: 10.1074/jbc.m116.756205] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Revised: 10/13/2016] [Indexed: 11/06/2022] Open
Abstract
Folding of proteins usually involves intermediates, of which an important type is the molten globule (MG). MGs are ensembles of interconverting conformers that contain (non-)native secondary structure and lack the tightly packed tertiary structure of natively folded globular proteins. Whereas MGs of various purified proteins have been probed to date, no data are available on their presence and/or effect during protein synthesis. To study whether MGs arise during translation, we use ribosome-nascent chain (RNC) complexes of the electron transfer protein flavodoxin. Full-length isolated flavodoxin, which contains a non-covalently bound flavin mononucleotide (FMN) as cofactor, acquires its native α/β parallel topology via a folding mechanism that contains an off-pathway intermediate with molten globular characteristics. Extensive population of this MG state occurs at physiological ionic strength for apoflavodoxin variant F44Y, in which a phenylalanine at position 44 is changed to a tyrosine. Here, we show for the first time that ascertaining the binding rate of FMN as a function of ionic strength can be used as a tool to determine the presence of the off-pathway MG on the ribosome. Application of this methodology to F44Y apoflavodoxin RNCs shows that at physiological ionic strength the ribosome influences formation of the off-pathway MG and forces the nascent chain toward the native state.
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Affiliation(s)
- Joseline A Houwman
- From the Laboratory of Biochemistry, Wageningen University, 6708 WE Wageningen, The Netherlands
| | - Estelle André
- From the Laboratory of Biochemistry, Wageningen University, 6708 WE Wageningen, The Netherlands
| | - Adrie H Westphal
- From the Laboratory of Biochemistry, Wageningen University, 6708 WE Wageningen, The Netherlands
| | - Willem J H van Berkel
- From the Laboratory of Biochemistry, Wageningen University, 6708 WE Wageningen, The Netherlands
| | - Carlo P M van Mierlo
- From the Laboratory of Biochemistry, Wageningen University, 6708 WE Wageningen, The Netherlands
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10
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Structural basis of urea-induced unfolding: Unraveling the folding pathway of hemochromatosis factor E. Int J Biol Macromol 2016; 91:1051-61. [DOI: 10.1016/j.ijbiomac.2016.06.055] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 06/16/2016] [Accepted: 06/17/2016] [Indexed: 12/16/2022]
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11
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DeForte S, Uversky VN. Intrinsically disordered proteins in PubMed: what can the tip of the iceberg tell us about what lies below? RSC Adv 2016. [DOI: 10.1039/c5ra24866c] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Papers that use IDP terminology represent only the tip of the iceberg of the larger body of literature on this subject.
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Affiliation(s)
- Shelly DeForte
- Department of Molecular Medicine
- Morsani College of Medicine
- University of South Florida
- Tampa
- USA
| | - Vladimir N. Uversky
- Department of Molecular Medicine
- Morsani College of Medicine
- University of South Florida
- Tampa
- USA
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12
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Naiyer A, Hassan MI, Islam A, Sundd M, Ahmad F. Structural characterization of MG and pre-MG states of proteins by MD simulations, NMR, and other techniques. J Biomol Struct Dyn 2015; 33:2267-84. [PMID: 25586676 DOI: 10.1080/07391102.2014.999354] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Almost all proteins fold via a number of partially structured intermediates such as molten globule (MG) and pre-molten globule states. Understanding the structure of these intermediates at atomic level is often a challenge, as these states are observed under extreme conditions of pH, temperature, and chemical denaturants. Furthermore, several other processes such as chemical modification, site-directed mutagenesis (or point mutation), and cleavage of covalent bond of natural proteins often lead to MG like partially unfolded conformation. However, the dynamic nature of proteins in these states makes them unsuitable for most structure determination at atomic level. Intermediate states studied so far have been characterized mostly by circular dichroism, fluorescence, viscosity, dynamic light scattering measurements, dye binding, infrared techniques, molecular dynamics simulations, etc. There is a limited amount of structural data available on these intermediate states by nuclear magnetic resonance (NMR) and hence there is a need to characterize these states at the molecular level. In this review, we present characterization of equilibrium intermediates by biophysical techniques with special reference to NMR.
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Affiliation(s)
- Abdullah Naiyer
- a Centre for Interdisciplinary Research in Basic Sciences , Jamia Millia Islamia , Jamia Nagar, New Delhi - 110025 , India
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13
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Bychkova VE, Basova LV, Balobanov VA. How membrane surface affects protein structure. BIOCHEMISTRY (MOSCOW) 2015; 79:1483-514. [DOI: 10.1134/s0006297914130045] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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14
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Pulagam LP, Steinhoff HJ. Acidic pH-Induced Membrane Insertion of Colicin A into E. coli Natural Lipids Probed by Site-Directed Spin Labeling. J Mol Biol 2013; 425:1782-94. [DOI: 10.1016/j.jmb.2013.01.037] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2012] [Revised: 01/30/2013] [Accepted: 01/31/2013] [Indexed: 10/27/2022]
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15
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May KL, Yan Q, Tumer NE. Targeting ricin to the ribosome. Toxicon 2013; 69:143-51. [PMID: 23454625 DOI: 10.1016/j.toxicon.2013.02.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 02/01/2013] [Accepted: 02/06/2013] [Indexed: 12/15/2022]
Abstract
The plant toxin ricin is highly toxic for mammalian cells and is of concern for bioterrorism. Ricin belongs to a family of functionally related toxins, collectively referred to as ribosome inactivating proteins (RIPs), which disable ribosomes and halt protein synthesis. Currently there are no specific antidotes against ricin or related RIPs. The catalytic subunit of ricin is an N-glycosidase that depurinates a universally conserved adenine residue within the sarcin/ricin loop (SRL) of the 28S rRNA. This depurination activity inhibits translation and its biochemistry has been intensively studied. Yet, recent developments paint a more complex picture of toxicity, with ribosomal proteins and cellular signaling pathways contributing to the potency of ricin. In particular, several studies have now established the importance of the ribosomal stalk structure in facilitating the depurination activity and ribosome specificity of ricin and other RIPs. This review highlights recent developments defining toxin-ribosome interactions and examines the significance of these interactions for toxicity and therapeutic intervention.
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Affiliation(s)
- Kerrie L May
- Department of Plant Biology and Pathology, School of Environmental and Biological Sciences, Rutgers University, 59 Dudley Road, New Brunswick, NJ 08901-8520, USA
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16
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Singh VK, Rahman MN, Munro K, Uversky VN, Smith SP, Jia Z. Free cysteine modulates the conformation of human C/EBP homologous protein. PLoS One 2012; 7:e34680. [PMID: 22496840 PMCID: PMC3319616 DOI: 10.1371/journal.pone.0034680] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Accepted: 03/08/2012] [Indexed: 01/01/2023] Open
Abstract
The C/EBP Homologous Protein (CHOP) is a nuclear protein that is integral to the unfolded protein response culminating from endoplasmic reticulum stress. Previously, CHOP was shown to comprise extensive disordered regions and to self-associate in solution. In the current study, the intrinsically disordered nature of this protein was characterized further by comprehensive in silico analyses. Using circular dichroism, differential scanning calorimetry and nuclear magnetic resonance, we investigated the global conformation and secondary structure of CHOP and demonstrated, for the first time, that conformational changes in this protein can be induced by the free amino acid L-cysteine. Addition of L-cysteine caused a significant dose-dependent decrease in the protein helicity--dropping from 69.1% to 23.8% in the presence of 1 mM of L-cysteine--and a sequential transition to a more disordered state, unlike that caused by thermal denaturation. Furthermore, the presence of small amounts of free amino acid (80 µM, an 8:1 cysteine∶CHOP ratio) during CHOP thermal denaturation altered the molecular mechanism of its melting process, leading to a complex, multi-step transition. On the other hand, high levels (4 mM) of free L-cysteine seemed to cause a complete loss of rigid cooperatively melting structure. These results suggested a potential regulatory function of L-cysteine which may lead to changes in global conformation of CHOP in response to the cellular redox state and/or endoplasmic reticulum stress.
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Affiliation(s)
- Vinay K. Singh
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Mona N. Rahman
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Kim Munro
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Vladimir N. Uversky
- Department of Molecular Medicine, University of South Florida, Tampa, Florida, United States of America
- Institute for Biological Instrumentation, Russian Academy of Sciences, Pushchino, Moscow Region, Russia
| | - Steven P. Smith
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Zongchao Jia
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
- * E-mail:
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17
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Dave S, Mahajan S, Chandra V, Gupta P. Trifluoroethanol stabilizes the molten globule state and induces non-amyloidic turbidity in stem bromelain near its isoelectric point. Int J Biol Macromol 2011; 49:536-42. [DOI: 10.1016/j.ijbiomac.2011.06.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2011] [Revised: 06/03/2011] [Accepted: 06/07/2011] [Indexed: 11/28/2022]
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18
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Banerjee R, Reynolds NM, Yadavalli SS, Rice C, Roy H, Banerjee P, Alexander RW, Ibba M. Mitochondrial Aminoacyl-tRNA Synthetase Single-Nucleotide Polymorphisms That Lead to Defects in Refolding but Not Aminoacylation. J Mol Biol 2011; 410:280-93. [DOI: 10.1016/j.jmb.2011.05.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2011] [Revised: 05/05/2011] [Accepted: 05/06/2011] [Indexed: 12/28/2022]
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19
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Wei-Guo J, Chang-Wei L, Ji-Lin T, Zheng-Yan W, Shao-Jun D, Er-Kang W. Electrochemical and Spectroscopic Study on the Interaction of Cytochrome c with Anionic Lipid Vesicles. CHINESE J CHEM 2010. [DOI: 10.1002/cjoc.20030210514] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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20
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Balobanov VA, Il’ina NB, Katina NS, Kashparov IA, Dolgikh DA, Bychkova VE. Kinetics of interactions between apomyoglobin and phospholipid membrane. Mol Biol 2010. [DOI: 10.1134/s0026893310040187] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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21
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Uversky VN, Dunker AK. Understanding protein non-folding. BIOCHIMICA ET BIOPHYSICA ACTA 2010; 1804:1231-64. [PMID: 20117254 PMCID: PMC2882790 DOI: 10.1016/j.bbapap.2010.01.017] [Citation(s) in RCA: 901] [Impact Index Per Article: 64.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2009] [Revised: 01/09/2010] [Accepted: 01/21/2010] [Indexed: 02/07/2023]
Abstract
This review describes the family of intrinsically disordered proteins, members of which fail to form rigid 3-D structures under physiological conditions, either along their entire lengths or only in localized regions. Instead, these intriguing proteins/regions exist as dynamic ensembles within which atom positions and backbone Ramachandran angles exhibit extreme temporal fluctuations without specific equilibrium values. Many of these intrinsically disordered proteins are known to carry out important biological functions which, in fact, depend on the absence of a specific 3-D structure. The existence of such proteins does not fit the prevailing structure-function paradigm, which states that a unique 3-D structure is a prerequisite to function. Thus, the protein structure-function paradigm has to be expanded to include intrinsically disordered proteins and alternative relationships among protein sequence, structure, and function. This shift in the paradigm represents a major breakthrough for biochemistry, biophysics and molecular biology, as it opens new levels of understanding with regard to the complex life of proteins. This review will try to answer the following questions: how were intrinsically disordered proteins discovered? Why don't these proteins fold? What is so special about intrinsic disorder? What are the functional advantages of disordered proteins/regions? What is the functional repertoire of these proteins? What are the relationships between intrinsically disordered proteins and human diseases?
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Affiliation(s)
- Vladimir N Uversky
- Institute for Intrinsically Disordered Protein Research, Center for Computational Biology and Bioinformatics, Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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22
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Prudovsky I, Tarantini F, Landriscina M, Neivandt D, Soldi R, Kirov A, Small D, Kathir KM, Rajalingam D, Kumar TKS. Secretion without Golgi. J Cell Biochem 2008; 103:1327-43. [PMID: 17786931 PMCID: PMC2613191 DOI: 10.1002/jcb.21513] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
A growing number of proteins devoid of signal peptides have been demonstrated to be released through the non-classical pathways independent of endoplasmic reticulum and Golgi. Among them are two potent proangiogenic cytokines FGF1 and IL1alpha. Stress-induced transmembrane translocation of these proteins requires the assembly of copper-dependent multiprotein release complexes. It involves the interaction of exported proteins with the acidic phospholipids of the inner leaflet of the cell membrane and membrane destabilization. Not only stress, but also thrombin treatment and inhibition of Notch signaling stimulate the export of FGF1. Non-classical release of FGF1 and IL1alpha presents a promising target for treatment of cardiovascular, oncologic, and inflammatory disorders.
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Affiliation(s)
- Igor Prudovsky
- Maine Medical Center Research Institute, Maine Medical Center, Scarborough, Maine 04074, USA.
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23
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Molten globule and native state ensemble of Helicobacter pylori flavodoxin: can crowding, osmolytes or cofactors stabilize the native conformation relative to the molten globule? Biophys J 2008; 95:1913-27. [PMID: 18441031 DOI: 10.1529/biophysj.108.130153] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Partly unfolded protein conformations close in energy to the native state may be involved in protein functioning and also be related to folding diseases, but yet their structure and energetics are poorly understood. One such conformation, the monomeric and well-behaved molten globule of Helicobacter pylori apoflavodoxin, is here investigated to provide, in a wide pH interval, a complete thermodynamic description of its unfolding equilibrium and the equilibrium linking molten globule and native state. All thermodynamic and molecular properties of the molten globule here analyzed are characteristic of a partly unfolded conformation, and their differences with those of the native state are typically quantitative rather than qualitative. The stability data depict a native state ensemble where the relative populations of the different intermediates are strongly modulated by pH. Whereas the molten globule is dominant at pH 2.0, at neutral pH it is just the least stable of three partly unfolded intermediates populated by this protein. It is of interest that the energy rank of these intermediates at pH 7.0 is consistent with their likelihood to overcome the native state and become the more stable conformation when the native state protein is subjected to heat or mutation stress. Given the small volume difference between molten globule and native state, neither crowding agents nor osmolytes can drive the molten globule back to the native state. This observation, which is in qualitative accord with predictions of simple excluded volume theory, indicates that molecular crowding in vivo is not an effective mechanism to minimize partial unfolding events leading to equilibrium intermediates.
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Cremades N, Bueno M, Neira JL, Velázquez-Campoy A, Sancho J. Conformational Stability of Helicobacter pylori Flavodoxin. J Biol Chem 2008; 283:2883-95. [DOI: 10.1074/jbc.m705677200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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25
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Wieland JA, Gewirth AA, Leckband DE. Single-molecule measurements of the impact of lipid phase behavior on anchor strengths. J Phys Chem B 2007; 109:5985-93. [PMID: 16851653 DOI: 10.1021/jp045461b] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This work describes atomic force microscopy studies of the physical parameters determining the strength of lipid anchorage in bilayers as a function of the phase state of the lipid matrix. These investigations used biotinylated lipids and streptavidin-derivatized tips to quantify the lipid pullout force from different lipid matrices. Analysis of the data using both dynamic force spectroscopy and full microscopic models show that the anchorage strength is greater in gel-phase relative to fluid-phase lipids. Additional model parameter estimates provide further insights into the hidden energy barriers that determine the mechanical integrity of lipid anchors in biological membranes.
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Affiliation(s)
- Julie A Wieland
- Department of Chemistry, Department of Chemical and Biomolecular Engineering, and Fredrick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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26
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Chalton DA, Kelly IF, McGregor A, Ridley H, Watkinson A, Miller J, Lakey JH. Unfolding transitions of Bacillus anthracis protective antigen. Arch Biochem Biophys 2007; 465:1-10. [PMID: 17531947 DOI: 10.1016/j.abb.2007.04.030] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Revised: 04/24/2007] [Accepted: 04/24/2007] [Indexed: 10/23/2022]
Abstract
Protective antigen (PA) is an 83kDa protein which, although essential for toxicity of Bacillus anthracis, is harmless and an effective vaccine component. In vivo it undergoes receptor binding, proteolysis, heptamerisation and membrane insertion. Here we probe the response of PA to denaturants, temperature and pH. We present analyses (including barycentric mean) of the unfolding and refolding behavior of PA and reveal the origin of two critical steps in the denaturant unfolding pathway in which the first step is a calcium and pH dependent rearrangement of domain 1. Thermal unfolding fits a single transition near 50 degrees C. We show for the first time circular dichroism (CD) spectra of the heptameric, furin-cleaved PA63 and the low-pH forms of both PA83 and PA63. Although only PA63 should reach the acidic endosome, both PA83 and PA63 undergo similar acidic transitions and an unusual change from a beta II to a beta I CD spectrum.
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Affiliation(s)
- David A Chalton
- Institute of Cell and Molecular Biosciences, University of Newcastle upon Tyne, Framlington Place, Newcastle NE2 4HH, UK
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27
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Banerjee T, Kishore N. 2,2,2-Trifluoroethanol-Induced Molten Globule State of Concanavalin A and Energetics of 8-Anilinonaphthalene Sulfonate Binding: Calorimetric and Spectroscopic Investigation. J Phys Chem B 2005; 109:22655-62. [PMID: 16853949 DOI: 10.1021/jp053757r] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The interaction of 2,2,2-trifluoroethanol (TFE) with concanavalin A has been investigated by using a combination of differential scanning calorimetry, isothermal titration calorimetry (ITC), circular dichroism (CD), and fluorescence spectroscopy at pH 2.5 and 5.2. All of the calorimetric transitions at both the pH values were found to be irreversible. In the presence of 4 mol kg(-1) TFE at pH 2.5, concanavalin A is observed to be in a partially folded state with significant loss of native tertiary structure. The loss of specific side chain interactions in the transition from native to the TFE-induced partially folded state is demonstrated by the loss of cooperative thermal transition and reduction of the CD bands in the aromatic region. Acrylamide quenching, 8-anilinonaphthalene sulfonate (ANS) binding, and energy transfer also suggest that in the presence of 4 mol kg(-1) TFE at pH 2.5 concanavalin A is in a molten globule state. ITC has been used for the first time to characterize the energetics of ANS binding to the molten globule state. ITC results indicate that the binding of ANS to the molten globule state and acid-induced state at pH 2.5 displays heterogeneity with two classes of non-interacting binding sites. The results provide insights into the role of hydrophobic and electrostatic interactions in the binding of ANS to concanavalin A. The results also demonstrate that ITC can be used to characterize the partially folded states of the protein both qualitatively and quantitatively.
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Affiliation(s)
- Tuhina Banerjee
- Department of Chemistry, Indian Institute of Technology, Bombay, Powai, Mumbai 400 076, India
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28
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Raffy S, Lazdunski C, Teissié J. Electroinsertion and activation of the C-terminal domain of colicin A, a voltage gated bacterial toxin, into mammalian cell membranes. Mol Membr Biol 2005; 21:237-46. [PMID: 15371013 DOI: 10.1080/09687680410001711632] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The C-terminal fragment of colicin, a protein that is highly soluble in aqueous solution, is spontaneously and irreversibly inserted into the membranes of mammalian cells, which are locally permeabilized by a transmembrane voltage increase. Insertion is detected by immunodetection. This is obtained by mixing the protein with electropermeabilized cells. The same result is observed by pulsing the colicin/cell mixture. Electroinsertion is therefore obtained for the first time with a multi-fragment spanning protein. The cell viability is not affected beyond the effect of electropermeabilization. A train of low voltage repetitive transmembrane modulation, which cannot trigger membrane permeabilization, is applied a day after the electroinsertion. This induces no effect on unmodified cells but triggers the lysis of cells in which colicin has been inserted by the first electropulsation. The low-level electrical treatment is high enough to trigger the voltage gated opening of colicin and to induce the associated toxicity. A transmembrane configuration of colicin is therefore obtained by electroinsertion. The toxic effect of their voltage gating is only obtained when a critical number of voltage gated channels are activated.
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Affiliation(s)
- Sophie Raffy
- Institut de Pharmacologie et de Biologie Structurale du CNRS (UMR 5089), 205 route de Narbonne, F-31077 Toulouse cedex 4, France
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29
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Hamada D, Kato T, Ikegami T, Suzuki KN, Hayashi M, Murooka Y, Honda T, Yanagihara I. EspB from enterohaemorrhagic Escherichia coli is a natively partially folded protein. FEBS J 2005; 272:756-68. [PMID: 15670156 DOI: 10.1111/j.1742-4658.2004.04513.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The structural properties of EspB, a virulence factor of the Escherichia coli O157 type III secretion system, were characterized. Far-UV and near-UV CD spectra, recorded between pH 1.0 and pH 7.0, show that the protein assumes alpha-helical structures and that some tyrosine tertiary contacts may exist. All tyrosine side-chains are exposed to water, as determined by acrylamide fluorescence quenching spectroscopy. An increase in the fluorescence intensity of 8-anilinonaphthalene-1-sulfonate was observed at pH 2.0 in the presence of EspB, whereas no such increase in fluorescence was observed at pH 7.0. These data suggest the formation of a molten globule state at pH 2.0. Destabilization of EspB at low pH was shown by urea-unfolding transitions, monitored by far-UV CD spectroscopy. The result from a sedimentation equilibrium study indicated that EspB assumes a monomeric form at pH 7.0, although its Stokes radius (estimated by multiangle laser light scattering) was twice as large as expected for a monomeric globular structure of EspB. These data suggest that EspB, at pH 7.0, assumes a relatively expanded conformation. The chemical shift patterns of EspB 15N-1H heteronuclear single quantum correlation spectra at pH 2.0 and 7.0 are qualitatively similar to that of urea-unfolded EspB. Taken together, the properties of EspB reported here provide evidence that EspB is a natively partially folded protein, but with less exposed hydrophobic surface than traditional molten globules. This structural feature of EspB may be advantageous when EspB interacts with various biomolecules during the bacterial infection of host cells.
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Affiliation(s)
- Daizo Hamada
- Department of Developmental Infectious Diseases, Research Institute, Osaka Medical Center for Maternal and Child Health, Japan
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30
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Krantz BA, Trivedi AD, Cunningham K, Christensen KA, Collier RJ. Acid-induced unfolding of the amino-terminal domains of the lethal and edema factors of anthrax toxin. J Mol Biol 2005; 344:739-56. [PMID: 15533442 DOI: 10.1016/j.jmb.2004.09.067] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2004] [Revised: 09/22/2004] [Accepted: 09/23/2004] [Indexed: 11/22/2022]
Abstract
The two enzymatic components of anthrax toxin, lethal factor (LF) and edema factor (EF), are transported to the cytosol of mammalian cells by the third component, protective antigen (PA). A heptameric form of PA binds LF and/or EF and, under the acidic conditions encountered in endosomes, generates a membrane-spanning pore that is thought to serve as a passageway for these enzymes to enter the cytosol. The pore contains a 14-stranded transmembrane beta-barrel that is too narrow to accommodate a fully folded protein, necessitating that LF and EF unfold, at least partly, in order to pass. Here, we describe the pH-dependence of the unfolding of LF(N) and EF(N), the 30kDa N-terminal PA-binding domains, and minimal translocatable units, of LF and EF. Equilibrium chemical denaturation studies using fluorescence and circular dichroism spectroscopy show that each protein unfolds via a four-state mechanism: N<-->I<-->J<-->U. The acid-induced N-->I transition occurs within the pH range of the endosome (pH 5-6). The I state predominates at lower pH values, and the J and U states are populated significantly only in the presence of denaturant. The I state is compact and has characteristics of a molten globule, as shown by its retention of significant secondary structure and its ability to bind an apolar fluorophore. The N-->I transition leads to an overall 60% increase in buried surface area exposure. The J state is expanded significantly and has diminished secondary structure content. We analyze the different protonation states of LF(N) and EF(N) in terms of a linked equilibrium proton binding model and discuss the implications of our findings for the mechanism of acidic pH-induced translocation of anthrax toxin. Finally, analysis of the structure of the transmembrane beta-barrel of PA shows that it can accommodate alpha-helix, and we suggest that the steric constraints and composition of the lumen may promote alpha-helix formation.
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Affiliation(s)
- Bryan A Krantz
- Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Ave., Boston, MA 02115, USA
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31
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Naseem F, Khan RH. Fluoroalcohol-induced stabilization of the α-helical intermediates of lentil lectin: implication for non-hierarchical lectin folding. Arch Biochem Biophys 2004; 431:215-23. [PMID: 15488470 DOI: 10.1016/j.abb.2004.07.029] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2004] [Revised: 07/27/2004] [Indexed: 11/15/2022]
Abstract
An intermediate state of lentil lectin was characterized at pH 1 having low content of secondary as well as tertiary structure. Far- and near-UV CD spectroscopy showed loss of structure when pH was lowered from 7 to 0.8 but the structure loss was less than that of the protein in presence of 6M GndHCl. Intrinsic tryptophan fluorescence studies, ANS binding, and acrylamide quenching experiments supported the existence of the intermediate at low pH. The unfolding process of lentil lectin at pH 1 was also studied by GndHCl denaturation monitored by intrinsic fluorescence spectroscopy. The non-cooperative unfolding at pH 1, in contrast to cooperative unfolding of the native protein further confirmed the presence of loose tertiary structure. The unfolded structure of the lectin at pH 1 was also shown by limited tryptic digestion studies. Further studies were performed on this intermediate state of lentil lectin obtained at low pH in presence of fluoroalcohols 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoroisopropanol (HFIP). Lentil lectin is mainly a beta-sheet protein, and both TFE and HFIP stabilized the acid unfolded structure by inducing alpha-helical contacts. Interestingly, it was observed that induction of the non-native structure resulted in regain of protein activity to some extent. At pH 1, loss in activity was found with both dextran and bromelain while the reported intermediate at the given pH was found to regain activity with bromelain in presence of HFIP and TFE. HFIP induced more structure as compared to TFE and hence a greater regain in activity of about 30% was observed with HFIP as compared to a 15% regain with TFE. Activity with dextran in presence of fluoroalcohols could not be determined as turbidity developed in the corresponding blank preparations. Our results presented here point out the possibility of the formation of a helical structure preceding the formation of the native beta-sheet structure and thus support the non-hierarchical model of protein folding for lentil lectin.
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Affiliation(s)
- Farah Naseem
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202002, India
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32
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Lu H, Golovanov AP, Alcock F, Grossmann JG, Allen S, Lian LY, Tokatlidis K. The structural basis of the TIM10 chaperone assembly. J Biol Chem 2004; 279:18959-66. [PMID: 14973126 DOI: 10.1074/jbc.m313046200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tim9 and Tim10 are essential components of the "small Tim" family of proteins that facilitate insertion of polytopic proteins at the inner mitochondrial membrane. The small Tims are themselves imported from the cytosol and are organized in specific translocation assemblies in the intermembrane space. Their conformational properties and how these influence the mechanism of assembly remain poorly understood. Moreover, the three-dimensional structure of the TIM10 complex is unknown. We have characterized the structural properties of these proteins in their free and assembled states using NMR, circular dichroism, and small angle x-ray scattering. We show that the free proteins are largely unfolded in their reduced assembly-incompetent state and molten globules in their oxidized assembly-competent state. Tim10 appears less structured than Tim9 in their respective free oxidized forms and undergoes a larger structural change than Tim9 upon complexation. The NMR data here demonstrates unequivocally that only the oxidized states of the Tim9 and Tim10 proteins are capable of forming a complex. Zinc binding stabilizes the reduced state against proteolysis without significantly affecting the secondary structure. Solution x-ray scattering was used to obtain a molecular envelope for the subunits individually and for their fully functional TIM10 complex. Ab initio shape reconstructions based on the scattering data has allowed us to obtain the first low resolution three-dimensional structure of the TIM10 complex. This is a novel structure that displays extensive surface hydrophobicity. The structure also provides an explanation for the escorting function of this non-ATP-powered chaperone particle.
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Affiliation(s)
- Hui Lu
- School of Biological Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
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33
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Chattopadhyay K, Banerjee KK. Unfolding of Vibrio cholerae hemolysin induces oligomerization of the toxin monomer. J Biol Chem 2003; 278:38470-5. [PMID: 12878594 DOI: 10.1074/jbc.m305965200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vibrio cholerae hemolysin (HlyA) is a pore-forming toxin that exists in two stable forms: a hemolytically active water-soluble monomer with a native molecular weight of 65,000 and a hemolytically inactive SDS-stable heptamer with the configuration of a transmembrane diffusion channel. Transformation of the monomer into the oligomer is spontaneous but very slow in the absence of interaction with specific membrane components like cholesterol and sphingolipids. In this report, we show that mild disruption of the native tertiary structure of HlyA by 1.75 M urea triggered rapid and quantitative conversion of the monomer to an oligomer. Furthermore, the HlyA monomer when unfolded in 8 M urea refolded and reconstituted on renaturation into the oligomer biochemically and functionally similar to the heptamer formed in target lipid bilayer, suggesting that the HlyA polypeptide had a strong propensity to adopt the oligomer as the stable native state in preference to the monomer. On the basis of our results, we propose that (a) the hemolytically active HlyA monomer represents a quasi-stable conformation corresponding to a local free energy minimum and the transmembrane heptameric pore represents a stable conformation corresponding to an absolute free energy minimum and (b) any perturbation of the native tertiary structure of the HlyA monomer causing relaxation of conformational constraints tends to promote self-assembly to the oligomer with membrane components playing at most an accessory role.
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Affiliation(s)
- Kausik Chattopadhyay
- Division of Immunology and Vaccine Development, National Institute of Cholera And Enteric Diseases, Kolkata 700010, India
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34
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Sasahara K, McPhie P, Minton AP. Effect of dextran on protein stability and conformation attributed to macromolecular crowding. J Mol Biol 2003; 326:1227-37. [PMID: 12589765 DOI: 10.1016/s0022-2836(02)01443-2] [Citation(s) in RCA: 261] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Thermally induced transition curves of hen egg-white lysozyme were measured in the presence of several concentrations of dextran at pH 2.0 by near-UV and far-UV CD. The transition curves were fitted to a two-state model by a non-linear, least-squares method to obtain the transition temperature (T(m)), enthalpy change (deltaH(u)(T(m))), and free energy change (deltaG(u)(T)) of the unfolding transition. An increase in T(m) and almost constant deltaH(u)(T(m)) values were observed in the presence of added dextran at concentrations exceeding ca 100 g l(-1). In addition, dextran-induced conformational changes of fully unfolded protein were investigated by CD spectroscopy. Addition of high concentrations of dextran to solutions of acid-unfolded cytochrome c at pH 2.0 results in a shift of the CD spectrum from that characteristic of the fully unfolded polypeptide to that characteristic of the more compact, salt-induced molten globule state, a result suggesting that the molten globule-like state is stabilized relative to the fully unfolded form in crowded environments. Both observations are in qualitative accord with predictions of a previously proposed model for the effect of intermolecular excluded volume (macromolecular crowding) on protein stability and conformation.
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Affiliation(s)
- Kenji Sasahara
- Section on Physical Biochemistry, Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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35
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Huang S, Murphy S, Matouschek A. Effect of the protein import machinery at the mitochondrial surface on precursor stability. Proc Natl Acad Sci U S A 2000; 97:12991-6. [PMID: 11069283 PMCID: PMC27166 DOI: 10.1073/pnas.230243097] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Many biological processes require proteins to undergo conformational changes at the surface of membranes. For example, some precursor proteins unfold at the surface of mitochondria and chloroplasts before translocation into the organelles, and toxins such as colicin A unfold to the molten globule state at bacterial surfaces before inserting into the cell membrane. It is commonly thought that the membrane surfaces and the associated protein machinery destabilize the substrate proteins and that this effect is required for membrane insertion or translocation. One of the best characterized translocation processes is protein import into mitochondria. By measuring the contributions of individual interactions within a model protein to its stability at the mitochondrial surface and in free solution, we show here that the mitochondrial surface neither induces the molten globule state in this protein nor preferentially destabilizes any type of interaction (e.g., hydrogen bonds, nonpolar, etc.) within the protein. Because it is not possible to measure absolute protein stability at the surface of mitochondria, we determined the stability of a tightly associated protein-protein complex at the mitochondrial import site as a model of the stability of a protein. We found the binding constants of the protein-protein complex at the mitochondrial surface and in free solution to be identical. Our results demonstrate that the mitochondrial surface does not destabilize importing precursor proteins in its vicinity.
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Affiliation(s)
- S Huang
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, 2153 Sheridan Road, Evanston, IL 60208-3500, USA
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36
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Argent RH, Parrott AM, Day PJ, Roberts LM, Stockley PG, Lord JM, Radford SE. Ribosome-mediated folding of partially unfolded ricin A-chain. J Biol Chem 2000; 275:9263-9. [PMID: 10734065 DOI: 10.1074/jbc.275.13.9263] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
After endocytic uptake by mammalian cells, the cytotoxic protein ricin is transported to the endoplasmic reticulum, whereupon the A-chain must cross the lumenal membrane to reach its ribosomal substrates. It is assumed that membrane traversal is preceded by unfolding of ricin A-chain, followed by refolding in the cytosol to generate the native, biologically active toxin. Here we describe biochemical and biophysical analyses of the unfolding of ricin A-chain and its refolding in vitro. We show that native ricin A-chain is surprisingly unstable at pH 7.0, unfolding non-cooperatively above 37 degrees C to generate a partially unfolded state. This species has conformational properties typical of a molten globule, and cannot be refolded to the native state by manipulation of the buffer conditions or by the addition of a stem-loop dodecaribonucleotide or deproteinized Escherichia coli ribosomal RNA, both of which are substrates for ricin A-chain. By contrast, in the presence of salt-washed ribosomes, partially unfolded ricin A-chain regains full catalytic activity. The data suggest that the conformational stability of ricin A-chain is ideally poised for translocation from the endoplasmic reticulum. Within the cytosol, ricin A-chain molecules may then refold in the presence of ribosomes, resulting in ribosome depurination and cell death.
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Affiliation(s)
- R H Argent
- School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom
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Smyth MG, Sumner IG, Lax AJ. Reduced pH causes structural changes in the potent mitogenic toxin of Pasteurella multocida. FEMS Microbiol Lett 1999; 180:15-20. [PMID: 10547439 DOI: 10.1111/j.1574-6968.1999.tb08772.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Pasteurella multocida toxin is a potent mitogen that is believed to act intracellularly. On transverse urea gradient gels at pH 8.0 the toxin displayed one major unfolding transition at 4 M urea. However, at pH 6.1 the unfolding transition took place at 3.5 M urea. Circular dichroism spectra also indicated that a structural change took place at acidic pH. In addition it was found that the toxin that had been denatured in 8 M urea refolded in solution with a high recovery of biological activity. These findings are discussed in terms of the likely domain structure of the P. multocida toxin.
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Affiliation(s)
- M G Smyth
- Institute of Food Research, Whiteknights Road, Reading, Berkshire, UK
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38
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Affiliation(s)
- M Fivaz
- Dept of Biochemistry, University of Geneva, 30 quai E. Ansermet, 1211 Geneva 4, Switzerland
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39
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Gažová Z, Antalı́k M, Bágel’ová J, Tomori Z. Effect of ionic strength on the interfacial properties of cytochrome c. ACTA ACUST UNITED AC 1999. [DOI: 10.1016/s0167-4838(99)00091-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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40
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Schwartz MP, Huang S, Matouschek A. The structure of precursor proteins during import into mitochondria. J Biol Chem 1999; 274:12759-64. [PMID: 10212260 DOI: 10.1074/jbc.274.18.12759] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Precursor proteins must be at least partially unfolded during import into mitochondria, but their actual conformation during translocation is not known. Are proteins fully unfolded and threaded through the import machinery amino acid by amino acid, or do they retain some partial structure? The folding pathway of most proteins in vitro contains a partially folded intermediate known as the molten globule state, and it has been suggested that proteins are in the molten globule state during translocation across membranes. Here we show that precursors are normally fully unfolded during import into mitochondria. However, precursors containing residual structure can be imported, if less efficiently.
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Affiliation(s)
- M P Schwartz
- Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, Illinois 60208-3500, USA
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41
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Lecordier L, Mercier C, Sibley LD, Cesbron-Delauw MF. Transmembrane insertion of the Toxoplasma gondii GRA5 protein occurs after soluble secretion into the host cell. Mol Biol Cell 1999; 10:1277-87. [PMID: 10198072 PMCID: PMC25268 DOI: 10.1091/mbc.10.4.1277] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The intracellular parasite Toxoplasma gondii resides within a specialized compartment, the parasitophorous vacuole (PV), that resists fusion with host cell endocytic and lysosomal compartments. The PV is extensively modified by secretion of parasite proteins, including the dense granule protein GRA5 that is specifically targeted to the delimiting membrane of the PV (PVM). We show here that GRA5 is present both in a soluble form and in hydrophobic aggregates. GRA5 is secreted as a soluble form into the PV after which it becomes stably associated with the PVM. Topological studies demonstrated that GRA5 was inserted into the PVM as a transmembrane protein with its N-terminal domain extending into the cytoplasm and its C terminus in the vacuole lumen. Deletion of 8 of the 18 hydrophobic amino acids of the single predicted transmembrane domain resulted in the failure of GRA5 to associate with the PVM; yet it remained correctly packaged in the dense granules and was secreted as a soluble protein into the PV. Collectively, these studies demonstrate that the secretory pathway in Toxoplasma is unusual in two regards; it allows soluble export of proteins containing typical transmembrane domains and provides a mechanism for their insertion into a host cell membrane after secretion from the parasite.
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Affiliation(s)
- L Lecordier
- Mécanismes Moléculaires de la Pathogénèse des Sporozoaires, Institut Pasteur de Lille, Institut de Biologie de Lille, 59019 Lille cedex, France
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42
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Blum O, Haiek A, Cwikel D, Dori Z, Meade TJ, Gray HB. Isolation of a myoglobin molten globule by selective cobalt(III)-induced unfolding. Proc Natl Acad Sci U S A 1998; 95:6659-62. [PMID: 9618468 PMCID: PMC22589 DOI: 10.1073/pnas.95.12.6659] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Reaction of the Schiff-base complex [Co(acetylacetonate-ethylenediimine)(NH3)2]+ with metmyoglobin at pH 6.5 yields a partially folded protein containing six Co(III) complexes. Although half of its alpha-helical secondary structure is retained, absorption and CD spectra indicate that the tertiary structure in both B-F and AGH domains is disrupted in the partially folded protein. In analogy to proton-induced unfolding, it is likely that the loss of tertiary structure is triggered by metal-ion binding to histidines. Cobalt(III)-induced unfolding of myoglobin is unique in its selectivity (other proteins are unaffected) and in allowing the isolation of the partially folded macromolecule (the protein does not refold or aggregate upon removal of free denaturant).
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Affiliation(s)
- O Blum
- Beckman Institute 139-74, California Institute of Technology, Pasadena, CA 91125, USA
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43
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Haddaoui EA, Leloup L, Petit-Glatron MF, Chambert R. Characterization of a stable intermediate trapped during reversible refolding of Bacillus subtilis alpha-amylase. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 249:505-9. [PMID: 9370360 DOI: 10.1111/j.1432-1033.1997.00505.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Bacillus subtilis exocellular alpha-amylase is reversibly refolded after denaturation by guanidine hydrochloride at pH 7 and 37 degrees C. The unfolding-folding transition monitored by intrinsic fluorescence changes and resistance to proteolysis was resolved into a two-state transition. The first step (t1/2 < 1 s) led from D, the totally unfolded state, to C, a stable partially structured state of the protein. This folding intermediate was devoid of any enzyme activity and partially resistant to protease degradation. Calcium was required for the transition from C to N, the native state. This metal did not remain associated with the native form and could be replaced by barium or strontium, but not by magnesium. We discuss the hypothesis that C, the folding intermediate whose further transformation is under kinetic control, is the competent state involved in the secretion process of alpha-amylase.
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Affiliation(s)
- E A Haddaoui
- Institut Jacques Monod, Laboratoire Génétique et Membranes, Centre National de la Recherche Scientifique, Université Paris 7, France
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44
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Lesieur C, Vécsey-Semjén B, Abrami L, Fivaz M, Gisou van der Goot F. Membrane insertion: The strategies of toxins (review). Mol Membr Biol 1997; 14:45-64. [PMID: 9253764 DOI: 10.3109/09687689709068435] [Citation(s) in RCA: 130] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Protein toxins are soluble molecules secreted by pathogenic bacteria which act at the plasma membrane or in the cytoplasm of target cells. They must therefore interact with a membrane at some point, either to modify its permeability properties or to reach the cytoplasm. As a consequence, toxins have the built-in capacity to adopt two generally incompatible states: water-soluble and transmembrane. Irrespective of their origin or function, the membrane interacting domain of most protein toxins seems to have adopted one out of two structural strategies to be able to undergo this metamorphosis. In the first group of toxins the membrane interacting domain has the structural characteristics of most known membrane proteins, i.e. it contains hydrophobic and amphipathic alpha-helices long enough to span a membrane. To render this 'membrane protein' water-soluble during the initial part of its life the hydrophobic helices are sheltered from the solvent by a barrel of amphipathic helices. In the second group of toxins the opposite strategy is adopted. The toxin is an intrinsically soluble protein and is composed mainly of beta-structure. These toxins manage to become membrane proteins by oligomerizing in order to combine amphipathic beta-sheet to generate sufficient hydrophobicity for membrane insertion to occur. Toxins from this latter group are thought to perforate the lipid bilayer as a beta-barrel such as has been described for bacterial porins, and has recently been shown for staphylococcal alpha-toxin. The two groups of toxins will be described in detail through the presentation of examples. Particular attention will be given to the beta-structure toxins, since four new structures have been solved over the past year: the staphyloccocal alpha-toxin channel, the anthrax protective antigen protoxin, the anthrax protective antigen-soluble heptamer and the CytB protoxin. Structural similarities with mammalian proteins implicated in the immune response and apoptosis will be discussed. Peptide toxins will not be covered in this review.
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Affiliation(s)
- C Lesieur
- Département de Biochimie, Faculté des Sciences, Genève, Switzerland
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Vécsey-Semjén B, Möllby R, van der Goot FG. Partial C-terminal unfolding is required for channel formation by staphylococcal alpha-toxin. J Biol Chem 1996; 271:8655-60. [PMID: 8621496 DOI: 10.1074/jbc.271.15.8655] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The pore-forming alpha-toxin from Staphylococcus aureus is secreted as a soluble monomeric protein. In order to form a transmembrane channel, the protein has to undergo oligomerization and membrane insertion. Previous studies have shown that channel formation is favored by acidic pH. We have analyzed the effect of pH on the kinetics of channel formation as well as on the conformation of the toxin. Using a variety of spectroscopic probes for protein structure, we have shown that alpha-toxin unfolded upon acidification and that the unfolding process occurred in at least three steps. The various steps could be selectively affected by modifying the salt concentration or the temperature. This unfolding was, however, only partial as the secondary structure remained native-like as witnessed by far UV CD measurements. The first unfolding step, corresponding to a region of the C-terminal half of the toxin, is of particular importance as it coincided with the exposure of hydrophobic patches on the surface of the protein as well as with the onset of channel formation. Our observations strongly suggest that transition of the C-terminal half of alpha-toxin to a molten globule-like state is required for channel formation.
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Affiliation(s)
- B Vécsey-Semjén
- Département de Biochimie, Université de Genève, 30 quai E. Ansermet, 1211 Genève, Switzerland
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46
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Ptitsyn OB, Bychkova VE, Uversky VN. Kinetic and equilibrium folding intermediates. Philos Trans R Soc Lond B Biol Sci 1995; 348:35-41. [PMID: 7770484 DOI: 10.1098/rstb.1995.0043] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Our recent experiments on the molten globule state and other protein folding intermediates lead to following conclusions: (i) the molten globule is separated by intramolecular first-order phase transitions from the native and unfolded states and therefore is a specific thermodynamic state of protein molecules; (ii) the novel equilibrium folding intermediate (the 'pre-molten globule' state) exists which can be similar to the 'burst' kinetic intermediate of protein folding; (iii) proteins denature and release their non-polar ligands at moderately low pH and moderately low dielectric constant, i.e. under conditions which may be related to those near membranes.
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Affiliation(s)
- O B Ptitsyn
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region
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47
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Affiliation(s)
- O B Ptitsyn
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region, Russia
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48
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Affiliation(s)
- A L Fink
- Department of Chemistry and Biochemistry, University of California, Santa Cruz 95064
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49
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el Kouhen R, Hoenger A, Engel A, Pagès JM. In vitro approaches to investigation of the early steps of colicin-OmpF interaction. EUROPEAN JOURNAL OF BIOCHEMISTRY 1994; 224:723-8. [PMID: 7925390 DOI: 10.1111/j.1432-1033.1994.0723a.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The OmpF porin plays a central role during the colicin uptake by sensitive Escherichia coli cells. Lipopolysaccharide-OmpF complexes (-1bLPS-OmpF), which contain one tightly bound and no loosely bound LPS molecules for each porin trimer, is able to recognize and bind to immobilized colicins. This association is specific to colicins A and N, which both use the OmpF porin as receptor, and depends on the presence of the porin-receptor domain on the bacteriocin molecule. The -1bLPS-OmpF complex protects sensitive cells against colicin A and N activity. The protection level depends on the native conformation, as demonstrated by heat denaturation of the trimeric porin which abolishes the protection. This indicates that the purified OmpF trimer presents an affinity site for the colicin which efficiently mimics the native cellular receptor site. These results are discussed with regard to the conformation of the receptor site and to the early steps of colicin uptake.
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Affiliation(s)
- R el Kouhen
- Enveloppe et permeation chez les enterobacteries, LIDSM-UPR 9027, CBBM CNRS, Marseille, France
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50
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Butko P, Cournoyer M, Pusztai-Carey M, Surewicz WK. Membrane interactions and surface hydrophobicity of Bacillus thuringiensis delta-endotoxin CryIC. FEBS Lett 1994; 340:89-92. [PMID: 8119414 DOI: 10.1016/0014-5793(94)80178-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The interaction between Bacillus thuringiensis insecticidal delta-endotoxin CryIC and phospholipid vesicles was studied by fluorescence spectroscopy. The toxin dissipates the diffusion potential across vesicular membranes, presumably by creating ion permeable channels or pores. This effect is pH-dependent and strongly increases under acidic conditions. The enhanced membrane-perturbing activity of CryIC at low pH correlates with the increased surface hydrophobicity of the toxin molecule. The membrane permeabilizing effect of the toxin is further increased by the presence of acidic phospholipids. These findings are discussed in relation to the mode of insecticidal action of the toxin.
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Affiliation(s)
- P Butko
- Institute for Biological Sciences, National Research Council, Ottawa, Ontario, Canada
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