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Liu D, Zhan Y, Wu X, Qiao H, Zhang Y, Li B. Design, preparation and characterization of octopus-like self-releasing intracellular protein transporter LEB5 based on Escherichia coli heat-labile enterotoxin. Int J Biol Macromol 2023; 237:124172. [PMID: 36966860 DOI: 10.1016/j.ijbiomac.2023.124172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Revised: 03/16/2023] [Accepted: 03/21/2023] [Indexed: 04/03/2023]
Abstract
Despite the great potential of protein drugs as intracellular therapeutic agents, the unmet challenge in breaking through the cell membrane barrier and delivering them to intracellular targets remains. Therefore, developing safe and effective delivery vehicles is critical for fundamental biomedical research and clinical applications. In this study, we designed an octopus-like self-releasing intracellular protein transporter, the LEB5, based on the heat-labile enterotoxin. This carrier comprises five identical units, each of which has three main components: a linker, a self-releasing enzyme sensitivity loop, and the LTB transport domain. The LEB5 comprises five purified monomers that self-assemble to create a pentamer with ganglioside GM1 binding capacity. The fluorescent protein EGFP was used as a reporter system to identify the LEB5 features. The high-purity fusion protein ELEB monomer was produced from modified bacteria carrying pET24a(+)-eleb recombinant plasmids. EGFP protein could effectively detach from LEB5 by low dosage trypsin, according to electrophoresis analysis. The transmission electron microscopy results indicate that both LEB5 and ELEB5 pentamers exhibit a relatively regularly spherical shape, and the differential scanning calorimetry measurements further suggest that these proteins possess excellent thermal stability. Fluorescence microscopy revealed that LEB5 translocated EGFP into different cell types. Flow cytometry showed cellular differences in the transport capacity of LEB5. According to the confocal microscopy, fluorescence analysis and western blotting data, EGFP was transferred to the endoplasmic reticulum by the LEB5 carrier, detached from LEB5 by cleavage of the enzyme-sensitive loop, and released into the cytoplasm. Within the dosage range of LEB5 10-80 μg/mL, cell counting kit-8 assay revealed no significant changes in cell viability. These results demonstrated that LEB5 is a safe and effective intracellular self-releasing delivery vehicle capable of transporting and releasing protein medicines into cells.
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Affiliation(s)
- Di Liu
- College of Biological Sciences and Technology and Center for Veterinary Medicine, Taiyuan Normal University, Jinzhong 030619, Shanxi, China.
| | - Yafen Zhan
- College of Biological Sciences and Technology and Center for Veterinary Medicine, Taiyuan Normal University, Jinzhong 030619, Shanxi, China
| | - Xiaoying Wu
- College of Biological Sciences and Technology and Center for Veterinary Medicine, Taiyuan Normal University, Jinzhong 030619, Shanxi, China
| | - Hongping Qiao
- College of Biological Sciences and Technology and Center for Veterinary Medicine, Taiyuan Normal University, Jinzhong 030619, Shanxi, China
| | - Yeli Zhang
- College of Biological Sciences and Technology and Center for Veterinary Medicine, Taiyuan Normal University, Jinzhong 030619, Shanxi, China
| | - Bo Li
- College of Biological Sciences and Technology and Center for Veterinary Medicine, Taiyuan Normal University, Jinzhong 030619, Shanxi, China; School of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi, China.
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2
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Bourgeat L, Pacini L, Serghei A, Lesieur C. Experimental diagnostic of sequence-variant dynamic perturbations revealed by broadband dielectric spectroscopy. Structure 2021; 29:1419-1429.e3. [PMID: 34051139 DOI: 10.1016/j.str.2021.05.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 03/23/2021] [Accepted: 05/07/2021] [Indexed: 02/08/2023]
Abstract
Genetic diversity leads to protein robustness, adaptability, and failure. Some sequence variants are structurally robust but functionally disturbed because mutations bring the protein onto unfolding/refolding routes resulting in misfolding diseases (e.g., Parkinson). We assume dynamic perturbations introduced by mutations foster the alternative unfolding routes and test this possibility by comparing the unfolding dynamics of the heat-labile enterotoxin B pentamers and the cholera toxin B pentamers, two pentamers structurally and functionally related and robust to 17 sequence variations. The B-subunit thermal unfolding dynamics are monitored by broadband dielectric spectroscopy in nanoconfined and weakly hydrated conditions. Distinct dielectric signals reveal the different B-subunits unfolding dynamics. Combined with network analyses, the experiments pinpoint the role of three mutations A1T, E7D, and E102A, in diverting LTB5 to alternative unfolding routes that protect LTB5 from dissociation. Altogether, the methodology diagnoses dynamics faults that may underlie functional disorder, drug resistance, or higher virulence of sequence variants.
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Affiliation(s)
- Laëtitia Bourgeat
- Univ Lyon, CNRS, INSA Lyon, Université Claude Bernard Lyon 1, Ecole Centrale de Lyon, Ampère, UMR5005, 69622 Villeurbanne, France; Univ Lyon, CNRS, IMP, 69622, Villeurbanne, France
| | - Lorenza Pacini
- Univ Lyon, CNRS, INSA Lyon, Université Claude Bernard Lyon 1, Ecole Centrale de Lyon, Ampère, UMR5005, 69622 Villeurbanne, France; Institut Rhônalpin des systèmes complexes, IXXI-ENS-Lyon, 69007, Lyon, France
| | | | - Claire Lesieur
- Univ Lyon, CNRS, INSA Lyon, Université Claude Bernard Lyon 1, Ecole Centrale de Lyon, Ampère, UMR5005, 69622 Villeurbanne, France; Institut Rhônalpin des systèmes complexes, IXXI-ENS-Lyon, 69007, Lyon, France.
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3
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Krause M, Sessler K, Kaziales A, Grahl R, Noettger S, Barth H, Schmidt H. Variants of Escherichia coli Subtilase Cytotoxin Subunits Show Differences in Complex Formation In Vitro. Toxins (Basel) 2019; 11:toxins11120703. [PMID: 31816894 PMCID: PMC6950094 DOI: 10.3390/toxins11120703] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 11/19/2019] [Accepted: 11/27/2019] [Indexed: 12/11/2022] Open
Abstract
The subtilase cytotoxin (SubAB) of Shiga toxin-producing Escherichia coli (STEC) is a member of the AB5 toxin family. In the current study, we analyzed the formation of active homo- and hetero-complexes of SubAB variants in vitro to characterize the mode of assembly of the subunits. Recombinant SubA1-His, SubB1-His, SubA2-2-His, and SubB2-2-His subunits, and His-tag-free SubA2-2 were separately expressed, purified, and biochemically characterized by circular dichroism (CD) spectroscopy, size-exclusion chromatography (SEC), and analytical ultracentrifugation (aUC). To confirm their biological activity, cytotoxicity assays were performed with HeLa cells. The formation of AB5 complexes was investigated with aUC and isothermal titration calorimetry (ITC). Binding of SubAB2-2-His to HeLa cells was characterized with flow cytometry (FACS). Cytotoxicity experiments revealed that the analyzed recombinant subtilase subunits were biochemically functional and capable of intoxicating HeLa cells. Inhibition of cytotoxicity by Brefeldin A demonstrated that the cleavage is specific. All His-tagged subunits, as well as the non-tagged SubA2-2 subunit, showed the expected secondary structural compositions and oligomerization. Whereas SubAB1-His complexes could be reconstituted in solution, and revealed a Kd value of 3.9 ± 0.8 μmol/L in the lower micromolar range, only transient interactions were observed for the subunits of SubAB2-2-His in solution, which did not result in any binding constant when analyzed with ITC. Additional studies on the binding characteristics of SubAB2-2-His on HeLa cells revealed that the formation of transient complexes improved binding to the target cells. Conclusively, we hypothesize that SubAB variants exhibit different characteristics in their binding behavior to their target cells.
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Affiliation(s)
- Maike Krause
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, Garbenstraße 28, University of Hohenheim, 70599 Stuttgart, Germany; (M.K.); (R.G.)
| | - Katharina Sessler
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081 Ulm, Germany; (K.S.); (S.N.); (H.B.)
| | - Anna Kaziales
- Center for Integrated Protein Science Munich, Department of Chemistry, Technical University of Munich, Lichtenbergstr. 4, 85748 Garching, Germany;
| | - Richard Grahl
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, Garbenstraße 28, University of Hohenheim, 70599 Stuttgart, Germany; (M.K.); (R.G.)
| | - Sabrina Noettger
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081 Ulm, Germany; (K.S.); (S.N.); (H.B.)
| | - Holger Barth
- Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081 Ulm, Germany; (K.S.); (S.N.); (H.B.)
| | - Herbert Schmidt
- Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, Garbenstraße 28, University of Hohenheim, 70599 Stuttgart, Germany; (M.K.); (R.G.)
- Correspondence: ; Tel.: +49-711-459-22305
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Glycan-deficient PrP stimulates VEGFR2 signaling via glycosaminoglycan. Cell Signal 2016; 28:652-62. [PMID: 27006333 DOI: 10.1016/j.cellsig.2016.03.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2016] [Revised: 03/18/2016] [Accepted: 03/18/2016] [Indexed: 12/23/2022]
Abstract
Whether the two N-linked glycans are important in prion, PrP, biology is unresolved. In Chinese hamster ovary (CHO) cells, the two glycans are clearly not important in the cell surface expression of transfected human PrP. Compared to fully-glycosylated PrP, glycan-deficient PrP preferentially partitions to lipid raft. In CHO cells glycan-deficient PrP also interacts with glycosaminoglycan (GAG) and vascular endothelial growth factor receptor 2 (VEGFR2), resulting in VEGFR2 activation and enhanced Akt phosphorylation. Accordingly, CHO cells expressing glycan-deficient PrP lacking the GAG binding motif or cells treated with heparinase to remove GAG show diminished Akt signaling. Being in lipid raft is critical, chimeric glycan-deficient PrP with CD4 transmembrane and cytoplasmic domains is absent in lipid raft and does not activate Akt signaling. CHO cells bearing glycan-deficient PrP also exhibit enhanced cellular adhesion and migration. Based on these findings, we propose a model in which glycan-deficient PrP, GAG, and VEGFR2 interact, activating VEGFR2 and resulting in changes in cellular behavior.
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Nag OK, Naciri J, Oh E, Spillmann CM, Delehanty JB. Lipid Raft-Mediated Membrane Tethering and Delivery of Hydrophobic Cargos from Liquid Crystal-Based Nanocarriers. Bioconjug Chem 2016; 27:982-93. [DOI: 10.1021/acs.bioconjchem.6b00042] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Okhil K. Nag
- Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Code 6900, 4555 Overlook Avenue SW, Washington, DC 20375, United States
| | - Jawad Naciri
- Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Code 6900, 4555 Overlook Avenue SW, Washington, DC 20375, United States
| | - Eunkeu Oh
- Optical Sciences Division, Naval Research Laboratory, Code 5600, 4555 Overlook Avenue SW, Washington, DC 20375, United States
- Sotera Defense Solutions, Inc., 7230 Lee DeForest Drive, Columbia, Maryland 21046, United States
| | - Christopher M. Spillmann
- Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Code 6900, 4555 Overlook Avenue SW, Washington, DC 20375, United States
| | - James B. Delehanty
- Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Code 6900, 4555 Overlook Avenue SW, Washington, DC 20375, United States
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6
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Debache K, Hemphill A. Differential effects of intranasal vaccination with recombinant NcPDI in different mouse models ofNeospora caninuminfection. Parasite Immunol 2012; 35:11-20. [DOI: 10.1111/pim.12013] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Accepted: 10/02/2012] [Indexed: 01/28/2023]
Affiliation(s)
- K. Debache
- Institute of Parasitology; Vetsuisse Faculty; University of Berne; Berne; Switzerland
| | - A. Hemphill
- Institute of Parasitology; Vetsuisse Faculty; University of Berne; Berne; Switzerland
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Zrimi J, Ng Ling A, Giri-Rachman Arifin E, Feverati G, Lesieur C. Cholera toxin B subunits assemble into pentamers--proposition of a fly-casting mechanism. PLoS One 2010; 5:e15347. [PMID: 21203571 PMCID: PMC3006222 DOI: 10.1371/journal.pone.0015347] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Accepted: 11/11/2010] [Indexed: 11/18/2022] Open
Abstract
The cholera toxin B pentamer (CtxB5), which belongs to the AB5 toxin family, is used as a model study for protein assembly. The effect of the pH on the reassembly of the toxin was investigated using immunochemical, electrophoretic and spectroscopic methods. Three pH-dependent steps were identified during the toxin reassembly: (i) acquisition of a fully assembly-competent fold by the CtxB monomer, (ii) association of CtxB monomer into oligomers, (iii) acquisition of the native fold by the CtxB pentamer. The results show that CtxB5 and the related heat labile enterotoxin LTB5 have distinct mechanisms of assembly despite sharing high sequence identity (84%) and almost identical atomic structures. The difference can be pinpointed to four histidines which are spread along the protein sequence and may act together. Thus, most of the toxin B amino acids appear negligible for the assembly, raising the possibility that assembly is driven by a small network of amino acids instead of involving all of them.
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Affiliation(s)
- Jihad Zrimi
- LAPTH, Université de Savoie, CNRS, Annecy le Vieux, France
| | - Alicia Ng Ling
- National University of Singapore, Physics Department, Singapore, Singapore
| | | | | | - Claire Lesieur
- LAPTH, Université de Savoie, CNRS, Annecy le Vieux, France
- National University of Singapore, Physics Department, Singapore, Singapore
- CEA-CNRS-Université Joseph Fourier, IRTSV, LBBSI, Grenoble, France
- * E-mail:
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Lack of lacto/neolacto-glycolipids enhances the formation of glycolipid-enriched microdomains, facilitating B cell activation. Proc Natl Acad Sci U S A 2010; 107:11900-5. [PMID: 20547865 DOI: 10.1073/pnas.0914298107] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In a previous study, we demonstrated that beta1,3-N-acetylglucosaminyltransferase 5 (B3gnt5) is a lactotriaosylceramide (Lc(3)Cer) synthase that synthesizes a precursor structure for lacto/neolacto-series glycosphingolipids (GSLs) in in vitro experiments. Here, we generated B3gnt5-deficient (B3gnt5(-/-)) mice to investigate the in vivo biological functions of lacto/neolacto-series GSLs. In biochemical analyses, lacto/neolacto-series GSLs were confirmed to be absent and no Lc(3)Cer synthase activity was detected in the tissues of these mice. These results demonstrate that beta3GnT5 is the sole enzyme synthesizing Lc(3)Cer in vivo. Ganglioside GM1, known as a glycosphingolipid-enriched microdomain (GEM) marker, was found to be up-regulated in B3gnt5(-/-) B cells by flow cytometry and fluorescence microscopy. However, no difference in the amount of GM1 was observed by TLC-immunoblotting analysis. The GEM-stained puncta on the surface of B3gnt5(-/-) resting B cells were brighter and larger than those of WT cells. These results suggest that structural alteration of GEM occurs in B3gnt5(-/-) B cells. We next examined whether BCR signaling-related proteins, such as BCR, CD19, and the signaling molecule Lyn, had moved into or out of the GEM fraction. In B3gnt5(-/-) B cells, these molecules were enriched in the GEM fraction or adjacent fraction. Moreover, B3gnt5(-/-) B cells were more sensitive to the induction of intracellular phosphorylation signals on BCR stimulation and proliferated more vigorously than WT B cells. Together, these results suggest that lacto/neolacto-series GSLs play an important role in clustering of GEMs and tether-specific proteins, such as BCR, CD19, and related signaling molecules to the GEMs.
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Mudrak B, Kuehn MJ. Heat-labile enterotoxin: beyond G(m1) binding. Toxins (Basel) 2010; 2:1445-70. [PMID: 22069646 PMCID: PMC3153253 DOI: 10.3390/toxins2061445] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Revised: 05/22/2010] [Accepted: 06/07/2010] [Indexed: 01/07/2023] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) is a significant source of morbidity and mortality worldwide. One major virulence factor released by ETEC is the heat-labile enterotoxin LT, which is structurally and functionally similar to cholera toxin. LT consists of five B subunits carrying a single catalytically active A subunit. LTB binds the monosialoganglioside GM1, the toxin’s host receptor, but interactions with A-type blood sugars and E. coli lipopolysaccharide have also been identified within the past decade. Here, we review the regulation, assembly, and binding properties of the LT B-subunit pentamer and discuss the possible roles of its numerous molecular interactions.
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Affiliation(s)
- Benjamin Mudrak
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA;
| | - Meta J. Kuehn
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
- Author to whom correspondence should be addressed; ; Tel.: +1-919-684-2545; Fax: +1-919-684-8885
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Samhan-Arias AK, Garcia-Bereguiain MA, Martin-Romero FJ, Gutierrez-Merino C. Clustering of plasma membrane-bound cytochrome b5 reductase within 'lipid raft' microdomains of the neuronal plasma membrane. Mol Cell Neurosci 2008; 40:14-26. [PMID: 17963686 DOI: 10.1016/j.mcn.2008.08.013] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Revised: 08/17/2008] [Accepted: 08/26/2008] [Indexed: 10/21/2022] Open
Abstract
Plasma membrane redox centres play a major role in neuronal defence against oxidative stress and survival. In cerebellar granule neurons in culture (CGN) a large pool of the flavoproteins are associated with the plasma membrane, and the intensity of CGN green/orange autofluorescence correlated with the levels of expression of cytochrome b(5) reductase. Regionalization of cytochrome b(5) reductase in the plasma membrane of CGN by fluorescence resonance energy transfer points out the close proximity between cytochrome b(5) reductase and the 'lipid raft' markers cholera toxin B and caveolin-2. This study unravels that membrane-bound cytochrome b(5) reductase is largely enriched at interneuronal contact sites in the neuronal soma and associated with 'lipid rafts' of the CGN plasma membrane. We also show that cytochrome b(5) reductase makes a large contribution to the NADH oxidase activity and to the red-shifted flavine fluorescence of purified rat brain synaptic plasma membranes. In conclusion, membrane-bound cytochrome b(5) reductase forms a large mesh of redox centres associated with the neuronal plasma membrane.
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Affiliation(s)
- Alejandro K Samhan-Arias
- Department of Biochemistry and Molecular Biology, Faculty of Sciences, University of Extremadura, Avda. de Elvas, s/n. 06071-Badajoz, Spain
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Zylberman V, Craig PO, Klinke S, Braden BC, Cauerhff A, Goldbaum FA. High Order Quaternary Arrangement Confers Increased Structural Stability to Brucella sp. Lumazine Synthase. J Biol Chem 2004; 279:8093-101. [PMID: 14660615 DOI: 10.1074/jbc.m312035200] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The penultimate step in the pathway of riboflavin biosynthesis is catalyzed by the enzyme lumazine synthase (LS). One of the most distinctive characteristics of this enzyme is the structural quaternary divergence found in different species. The protein exists as pentameric and icosahedral forms, built from practically the same structural monomeric unit. The pentameric structure is formed by five 18-kDa monomers, each extensively contacting neighboring monomers. The icosahedrical structure consists of 60 LS monomers arranged as 12 pentamers giving rise to a capsid exhibiting icosahedral 532 symmetry. In all lumazine synthases studied, the topologically equivalent active sites are located at the interfaces between adjacent subunits in the pentameric modules. The Brucella sp. lumazine synthase (BLS) sequence clearly diverges from pentameric and icosahedric enzymes. This unusual divergence prompted us to further investigate its quaternary arrangement. In the present work, we demonstrate by means of solution light scattering and x-ray structural analyses that BLS assembles as a very stable dimer of pentamers, representing a third category of quaternary assembly for lumazine synthases. We also describe by spectroscopic studies the thermodynamic stability of this oligomeric protein and postulate a mechanism for dissociation/unfolding of this macromolecular assembly. The higher molecular order of BLS increases its stability 20 degrees C compared with pentameric lumazine synthases. The decameric arrangement described in this work highlights the importance of quaternary interactions in the stabilization of proteins.
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Affiliation(s)
- Vanesa Zylberman
- Instituto Leloir, Consejo Nacional de Investigaciones Científicas y Técnicas and Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Patricias Argentinas 435 (C1405BWE), Buenos Aires, Argentina
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12
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Hartmann WK, Saptharishi N, Yang XY, Mitra G, Soman G. Characterization and analysis of thermal denaturation of antibodies by size exclusion high-performance liquid chromatography with quadruple detection. Anal Biochem 2004; 325:227-39. [PMID: 14751257 DOI: 10.1016/j.ab.2003.10.031] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Size exclusion chromatography (SEC) coupled with online light scattering, viscometry, refractometry, and UV-visible spectroscopy provides a very powerful tool for studying protein size, shape, and aggregation. This technique can be used to determine the molecular weight of the component peaks independent of the retention times in the SEC column and simultaneously measure the hydrodynamic radius and polydispersity of the protein. We applied this technology by coupling an Agilent Chemstation high-performance liquid chromatography system with a diode array UV-visible detector and a Viscotek 300 EZ Pro triple detector (combination of a light scattering detector, refractometer, and differential pressure viscometer) to characterize and compare the molecular properties of a number of monoclonal antibodies. Our studies reveal that different monoclonal immunoglobulin Gs (IgGs) and chimeric IgGs show slightly different retention times and therefore different molecular weights in gel filtration analysis. However, when they are analyzed by light scattering, refractometry, and viscometry, different IgGs have comparable molecular weight, molecular homogeneity (polydispersity), and size. Gel filtration coupled with UV or refractive index detection suggests that antibodies purified and formulated for preclinical and clinical development are more than 95% monomer with little or no detectable soluble aggregates. Light scattering measurements showed the presence of trace amounts of soluble aggregate in all the IgG preparations. The different IgG molecules showed different susceptibility to heat and pH. One of the murine antibodies was considerably less stable than the others at 55 degrees C. The application of this powerful technology for the characterization of monoclonal antibodies of therapeutic potential is discussed.
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Affiliation(s)
- Wanda K Hartmann
- Bioanalytical Development Laboratory, Biopharmaceutical Development Program, SAIC-Frederick, Inc., Frederick, MD 21702, USA
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Fraser SA, de Haan L, Hearn AR, Bone HK, Salmond RJ, Rivett AJ, Williams NA, Hirst TR. Mutant Escherichia coli heat-labile toxin B subunit that separates toxoid-mediated signaling and immunomodulatory action from trafficking and delivery functions. Infect Immun 2003; 71:1527-37. [PMID: 12595472 PMCID: PMC148879 DOI: 10.1128/iai.71.3.1527-1537.2003] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The homopentameric B-subunit components of Escherichia coli heat-labile enterotoxin (EtxB) and cholera toxin (CtxB) possess the capacity to enter mammalian cells and to activate cell-signaling events in leukocytes that modulate immune cell function. Both properties have been attributed to the ability of the B subunits to bind to GM1-ganglioside receptors, a ubiquitous glycosphingolipid found in the plasma membrane. Here we describe the properties of EtxB(H57S), a mutant B subunit with a His-->Ser substitution at position 57. The mutant was found to be severely defective in inducing leukocyte signaling, as shown by failure to (i) trigger caspase 3-mediated CD8(+)-T-cell apoptosis, (ii) activate nuclear translocation of NF-kappaB in Jurkat T cells, (iii) induce a potent anti-B-subunit response in mice, or (iv) serve as a mucosal adjuvant. However, its GM1 binding, cellular uptake, and delivery functions remained intact. This was further validated by the finding that EtxB(H57S) was as effective as EtxB in delivering a conjugated model class I epitope into the major histocompatibility complex class I pathway of a dendritic cell line. These observations imply that GM1 binding alone is not sufficient to trigger the signaling events responsible for the potent immunomodulatory properties of EtxB. Moreover, they demonstrate that its signaling properties play no role in EtxB uptake and trafficking. Thus, EtxB(H57S) represents a novel tool for evaluating the complex cellular interactions and signaling events occurring after receptor interaction, as well as offering an alternative means of delivering attached peptides in the absence of the potent immunomodulatory signals induced by wild-type B subunits.
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Affiliation(s)
- Sylvia A Fraser
- Department of Pathology & Microbiology, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, United Kingdom
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Jobling MG, Holmes RK. Mutational analysis of ganglioside GM(1)-binding ability, pentamer formation, and epitopes of cholera toxin B (CTB) subunits and CTB/heat-labile enterotoxin B subunit chimeras. Infect Immun 2002; 70:1260-71. [PMID: 11854209 PMCID: PMC127768 DOI: 10.1128/iai.70.3.1260-1271.2002] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Variants of cholera toxin B subunit (CTB) were made by bisulfite- and oligonucleotide-directed mutagenesis of the ctxB gene. Variants were screened by a radial passive immune hemolysis assay (RPIHA) for loss of binding to sheep erythrocytes (SRBC). Variant CTBs were characterized for the formation of immunoreactive pentamers, the ability to bind ganglioside GM(1) in vitro, and reactivity with a panel of monoclonal anti-CTB antibodies. Substitutions at eight positions (i.e., positions 22, 29, 36, 45, 64, 86, 93, and 100) greatly reduced the yield of immunoreactive CTB. RPIHA-negative substitution variants that formed immunoreactive pentamers were obtained for residues 12, 33, 36, 51, 52 + 54, 91, and 95. Tyrosine-12 was identified as a novel residue important for GM(1) binding since, among all of the novel variants isolated with altered RPIHA phenotypes, only CTB with aspartate substituted for tyrosine at position 12 failed to bind significantly to ganglioside GM(1) in vitro. In contrast, CTB variants with single substitutions for several other residues (Glu-51, Lys-91, and Ala-95) that participate in GM(1) binding, based on the crystal structure of CTB and the oligosaccharide of GM(1), were not appreciably altered in their ability to bind GM(1) in vitro, even though they showed altered RPIHA phenotypes and did not bind to SRBC. Hybrid B genes made by fusing ctxB and the related Escherichia coli heat-labile enterotoxin eltB genes at codon 56 produced CTB variants that had 7 or 12 heat-labile enterotoxin B residue substitutions in the amino or carboxyl halves of the monomer, respectively, each of which which also bound GM(1) as well as wild-type CTB. This collection of variant CTBs in which 47 of the 103 residues were substituted was used to map the epitopes of nine anti-CTB monoclonal antibodies (MAbs). Each MAb had a unique pattern of reactivity with the panel of CTB variants. Although no two of the epitopes recognized by different MAbs were identical, most of the single amino acid substitutions that altered the immunoreactivity of CTB affected more that one epitope. The tertiary structures of the epitopes of these anti-CTB MAbs are highly conformational and may involve structural elements both within and between CTB monomers. Substitution of valine for alanine at positions 10 and 46 had dramatic effects on the immunoreactivity of CTB, affecting epitopes recognized by eight or six MAbs, respectively.
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Affiliation(s)
- Michael G Jobling
- Department of Microbiology, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA
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