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Alcala-Torano R, Islam M, Cika J, Ho Lam K, Jin R, Ichtchenko K, Shoemaker CB, Van Deventer JA. Yeast Display Enables Identification of Covalent Single-Domain Antibodies against Botulinum Neurotoxin Light Chain A. ACS Chem Biol 2022; 17:3435-3449. [PMID: 36459441 PMCID: PMC10065152 DOI: 10.1021/acschembio.2c00574] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
While covalent drug discovery is reemerging as an important route to small-molecule therapeutic leads, strategies for the discovery and engineering of protein-based irreversible binding agents remain limited. Here, we describe the use of yeast display in combination with noncanonical amino acids (ncAAs) to identify irreversible variants of single-domain antibodies (sdAbs), also called VHHs and nanobodies, targeting botulinum neurotoxin light chain A (LC/A). Starting from a series of previously described, structurally characterized sdAbs, we evaluated the properties of antibodies substituted with reactive ncAAs capable of forming covalent bonds with nearby groups after UV irradiation (when using 4-azido-l-phenylalanine) or spontaneously (when using O-(2-bromoethyl)-l-tyrosine). Systematic evaluations in yeast display format of more than 40 ncAA-substituted variants revealed numerous clones that retain binding function while gaining either UV-mediated or spontaneous crosslinking capabilities. Solution-based analyses indicate that ncAA-substituted clones exhibit site-dependent target specificity and crosslinking capabilities uniquely conferred by ncAAs. Interestingly, not all ncAA substitution sites resulted in crosslinking events, and our data showed no apparent correlation between detected crosslinking levels and distances between sdAbs and LC/A residues. Our findings highlight the power of yeast display in combination with genetic code expansion in the discovery of binding agents that covalently engage their targets. This platform streamlines the discovery and characterization of antibodies with therapeutically relevant properties that cannot be accessed in the conventional genetic code.
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Affiliation(s)
- Rafael Alcala-Torano
- Chemical and Biological Engineering Department, Tufts University, Medford, Massachusetts 02155, United States of America
| | - Mariha Islam
- Chemical and Biological Engineering Department, Tufts University, Medford, Massachusetts 02155, United States of America
| | - Jaclyn Cika
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, New York 10016, United States of America
| | - Kwok Ho Lam
- Department of Physiology and Biophysics, University of California, Irvine, California 92697, United States of America
| | - Rongsheng Jin
- Department of Physiology and Biophysics, University of California, Irvine, California 92697, United States of America
| | - Konstantin Ichtchenko
- Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, New York 10016, United States of America
| | - Charles B. Shoemaker
- Tufts Cummings School of Veterinary Medicine, North Grafton, Massachusetts 01536, United States of America
| | - James A. Van Deventer
- Chemical and Biological Engineering Department, Tufts University, Medford, Massachusetts 02155, United States of America
- Biomedical Engineering Department, Tufts University, Medford, Massachusetts 02155, United States of America
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2
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Cai S, Kumar R, Singh BR. Clostridial Neurotoxins: Structure, Function and Implications to Other Bacterial Toxins. Microorganisms 2021; 9:2206. [PMID: 34835332 PMCID: PMC8618262 DOI: 10.3390/microorganisms9112206] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 10/19/2021] [Accepted: 10/19/2021] [Indexed: 01/20/2023] Open
Abstract
Gram-positive bacteria are ancient organisms. Many bacteria, including Gram-positive bacteria, produce toxins to manipulate the host, leading to various diseases. While the targets of Gram-positive bacterial toxins are diverse, many of those toxins use a similar mechanism to invade host cells and exert their functions. Clostridial neurotoxins produced by Clostridial tetani and Clostridial botulinum provide a classical example to illustrate the structure-function relationship of bacterial toxins. Here, we critically review the recent progress of the structure-function relationship of clostridial neurotoxins, including the diversity of the clostridial neurotoxins, the mode of actions, and the flexible structures required for the activation of toxins. The mechanism clostridial neurotoxins use for triggering their activity is shared with many other Gram-positive bacterial toxins, especially molten globule-type structures. This review also summarizes the implications of the molten globule-type flexible structures to other Gram-positive bacterial toxins. Understanding these highly dynamic flexible structures in solution and their role in the function of bacterial toxins not only fills in the missing link of the high-resolution structures from X-ray crystallography but also provides vital information for better designing antidotes against those toxins.
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Affiliation(s)
- Shuowei Cai
- Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, Dartmouth, MA 02747, USA
| | - Raj Kumar
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA 02747, USA; (R.K.); (B.R.S.)
| | - Bal Ram Singh
- Botulinum Research Center, Institute of Advanced Sciences, Dartmouth, MA 02747, USA; (R.K.); (B.R.S.)
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3
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Leka O, Wu Y, Li X, Kammerer RA. Crystal structure of the catalytic domain of botulinum neurotoxin subtype A3. J Biol Chem 2021; 296:100684. [PMID: 33891946 PMCID: PMC8135040 DOI: 10.1016/j.jbc.2021.100684] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 04/08/2021] [Accepted: 04/19/2021] [Indexed: 10/28/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) are among the most widely used therapeutic proteins; however, only two subtypes within the seven serotypes, BoNT/A1 and BoNT/B1, are currently used for medical and cosmetic applications. Distinct catalytic properties, substrate specificities, and duration of enzymatic activities potentially make other subtypes very attractive candidates to outperform conventional BoNTs in particular therapeutic applications. For example, BoNT/A3 has a significantly shorter duration of action than other BoNT/A subtypes. Notably, BoNT/A3 is the subtype with the least conserved catalytic domain among BoNT/A subtypes. This suggests that the sequence differences, many of which concern the α-exosite, contribute to the observed functional differences in toxin persistence by affecting the binding of the substrate SNAP-25 and/or the stability of the catalytic domain fold. To identify the molecular determinants accounting for the differences in the persistence observed for BoNT/A subtypes, we determined the crystal structure of the catalytic domain of BoNT/A3 (LC/A3). The structure of LC/A3 was found to be very similar to that of LC/A1, suggesting that the overall mode of SNAP-25 binding is common between these two proteins. However, circular dichroism (CD) thermal unfolding experiments demonstrated that LC/A3 is significantly less stable than LC/A1, implying that this might contribute to the reduced toxin persistence of BoNT/A3. These findings could be of interest in developing next-generation therapeutic toxins.
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Affiliation(s)
- Oneda Leka
- The Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - Yufan Wu
- The Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - Xiaodan Li
- The Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - Richard A Kammerer
- The Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer Institute, Villigen PSI, Switzerland.
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4
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Koike H, Kanda M, Hayashi H, Matsushima Y, Yoshikawa S, Ohba Y, Hayashi M, Nagano C, Sekimura K, Otsuka K, Kamiie J, Sasamoto T, Hashimoto T. Development of an alternative approach for detecting botulinum neurotoxin type A in honey: Analysis of non-toxic peptides with a reference labelled protein via liquid chromatography-tandem mass spectrometry. Food Addit Contam Part A Chem Anal Control Expo Risk Assess 2020; 37:1359-1373. [PMID: 32515305 DOI: 10.1080/19440049.2020.1766121] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
In this study, we developed a reference labelled protein containing the partial amino acid sequence of botulinum neurotoxin type A (BoNTA). We also applied it as an internal standard to detect specific and non-toxic peptides originated from BoNTA in honey with the use of liquid chromatography-tandem mass spectrometry (LC-MS/MS). Original proteins in the honey sample were collected through a two-step process that included solubilisation and trichloroacetic acid (TCA) precipitation. Solubilisation by adding water enabled processing of proteins in honey. TCA precipitation collected proteins without specific binding. The combination of protein alkylation and an appropriate enzyme-to-protein ratio ensured feasibility of tryptic digestion. A desalting process eliminated a large amount of salts and other tryptic peptides in the honey sample. The use of the reference labelled protein enabled compensation for tryptic digestion efficiency and electrospray ionisation efficiency based on LC-MS/MS measurement. After the peptide selection and protein BlastP analysis, five unique peptides were chosen. The non-toxic peptides originating from BoNTA were reliably detected using LC-MS/MS based on a multiple-reaction monitoring mode. Detection of several peptides ensured screening of BoNTA in honey samples. Based on the responses, the proteotypic peptide LYGIAINPNR was selected as the quantitative peptide. Due to maintaining the relative ion ratios, the selective transition completely identified the non-toxic peptides. The intensity of the transitions established a detection limit of BoNTA estimated to be 9.4 ng mL-1. Although extraction efficiency was not evaluated using the BoNTA standard, the results suggested this method may be used for quantification of BoNTA in honey. The method was applied to 19 honey samples purchased in Tokyo; none of them was found to contain the target toxin. Overall, the method is expected to accelerate BoNTA monitoring for food safety.
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Affiliation(s)
- Hiroshi Koike
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health , Tokyo, Japan
| | - Maki Kanda
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health , Tokyo, Japan
| | - Hairoshi Hayashi
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health , Tokyo, Japan
| | - Yoko Matsushima
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health , Tokyo, Japan
| | - Souichi Yoshikawa
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health , Tokyo, Japan
| | - Yumi Ohba
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health , Tokyo, Japan
| | - Momoka Hayashi
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health , Tokyo, Japan
| | - Chieko Nagano
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health , Tokyo, Japan
| | - Kotaro Sekimura
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health , Tokyo, Japan
| | - Kenji Otsuka
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health , Tokyo, Japan
| | - Junichi Kamiie
- Laboratory of Veterinary Pathology, School of Veterinary Medicine, Azabu University , Sagamihara, Japan
| | - Takeo Sasamoto
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health , Tokyo, Japan
| | - Tsuneo Hashimoto
- Department of Food Safety, Tokyo Metropolitan Institute of Public Health , Tokyo, Japan
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5
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Feltrup TM, Patel K, Kumar R, Cai S, Singh BR. A novel role of C-terminus in introducing a functionally flexible structure critical for the biological activity of botulinum neurotoxin. Sci Rep 2018; 8:8884. [PMID: 29891845 PMCID: PMC5995822 DOI: 10.1038/s41598-018-26764-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 05/17/2018] [Indexed: 02/06/2023] Open
Abstract
Botulinum neurotoxin (BoNT) is responsible for botulism, a clinical condition resulting in flaccid muscle paralysis and potentially death. The light chain is responsible for its intracellular toxicity through its endopeptidase activity. Available crystal structures of BoNT/A light chains (LCA) are based on various truncated versions (tLCA) of the full-length LCA (fLCA) and do not necessarily reflect the true structure of LCA in solution. The understanding of the mechanism of action, longevity of intoxication, and an improved development of endopeptidase inhibitors are dependent on first having a better insight into the structure of LCA in solution. Using an array of biophysical techniques, we report that the fLCA structure is significantly more flexible than tLCA in solution, which may be responsible for its dramatically higher enzymatic activity. This seems to be achieved by a much stronger, more rapid binding to substrate (SNAP-25) of the fLCA compared to tLCA. These results suggest that the C-terminus of LCA plays a critical role in introducing a flexible structure, which is essential for its biological function. This is the first report of such a massive structural role of the C-terminus of a protein being critical for maintaining a functional state.
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Affiliation(s)
- Thomas M Feltrup
- Department of Chemistry & Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA, 02747, USA
| | - Kruti Patel
- Department of Chemistry & Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA, 02747, USA
| | - Raj Kumar
- Botulinum Research Center, Institute of Advanced Sciences, North Dartmouth, MA, 02747, USA
| | - Shuowei Cai
- Department of Chemistry & Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA, 02747, USA
| | - Bal Ram Singh
- Botulinum Research Center, Institute of Advanced Sciences, North Dartmouth, MA, 02747, USA.
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6
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Scheps D, López de la Paz M, Jurk M, Hofmann F, Frevert J. Design of modified botulinum neurotoxin A1 variants with a shorter persistence of paralysis and duration of action. Toxicon 2017; 139:101-108. [PMID: 28918229 DOI: 10.1016/j.toxicon.2017.09.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 08/24/2017] [Accepted: 09/09/2017] [Indexed: 01/08/2023]
Abstract
Botulinum neurotoxins (BoNTs) are classified by their antigenic properties into seven serotypes (A-G) and in addition by their corresponding subtypes. They are further characterized by divergent onset and duration of effect. Injections of low doses of botulinum neurotoxins cause localized muscle paralysis that is beneficial for the treatment of several medical disorders and aesthetic indications. Optimizing the therapeutic properties could offer new treatment opportunities. This report describes a rational design approach to modify the pharmacological properties by mutations in the C-terminus of BoNT/A1 light chain (LC). Toxins with C-terminal modified LC's displayed an altered onset and duration of the paralytic effect in vivo. The level of effect was dependent on the kind of the mutation in the sequence of the C-terminus. A mutant with three mutations (T420E F423M Y426F) revealed a faster onset and a shorter duration than BoNT/A1 wild type (WT). It could be shown that the C-terminus of BoNT/A1-Lc controls both onset and duration of effect. Thus, it is possible to create a mutated BoNT/A1 with different pharmacological properties which might be useful in the therapy of new indications. This strategy opens the way to design BoNT variants with novel and useful properties.
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Affiliation(s)
- Daniel Scheps
- Merz Pharmaceuticals GmbH, Hermannswerder Haus 15, 14473, Potsdam, Germany
| | | | - Marcel Jurk
- Merz Pharmaceuticals GmbH, Hermannswerder Haus 15, 14473, Potsdam, Germany
| | - Fred Hofmann
- Merz Pharmaceuticals GmbH, Hermannswerder Haus 15, 14473, Potsdam, Germany
| | - Jürgen Frevert
- Merz Pharmaceuticals GmbH, Hermannswerder Haus 15, 14473, Potsdam, Germany.
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7
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Pirazzini M, Rossetto O, Eleopra R, Montecucco C. Botulinum Neurotoxins: Biology, Pharmacology, and Toxicology. Pharmacol Rev 2017; 69:200-235. [PMID: 28356439 PMCID: PMC5394922 DOI: 10.1124/pr.116.012658] [Citation(s) in RCA: 410] [Impact Index Per Article: 58.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The study of botulinum neurotoxins (BoNT) is rapidly progressing in many aspects.
Novel BoNTs are being discovered owing to next generation sequencing, but their
biologic and pharmacological properties remain largely unknown. The molecular
structure of the large protein complexes that the toxin forms with accessory
proteins, which are included in some BoNT type A1 and B1 pharmacological
preparations, have been determined. By far the largest effort has been dedicated to
the testing and validation of BoNTs as therapeutic agents in an ever increasing
number of applications, including pain therapy. BoNT type A1 has been also exploited
in a variety of cosmetic treatments, alone or in combination with other agents, and
this specific market has reached the size of the one dedicated to the treatment of
medical syndromes. The pharmacological properties and mode of action of BoNTs have
shed light on general principles of neuronal transport and protein-protein
interactions and are stimulating basic science studies. Moreover, the wide array of
BoNTs discovered and to be discovered and the production of recombinant BoNTs endowed
with specific properties suggest novel uses in therapeutics with increasing
disease/symptom specifity. These recent developments are reviewed here to provide an
updated picture of the biologic mechanism of action of BoNTs, of their increasing use
in pharmacology and in cosmetics, and of their toxicology.
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Affiliation(s)
- Marco Pirazzini
- Department of Biomedical Sciences, University of Padova, Italy (M.P., O.R., C.M.); Neurologic Department, University-Hospital S. Maria della Misericordia, Udine, Italy (R.E.); and Consiglio Nazionale delle Ricerche, Institute of Neuroscience, University of Padova, Italy (C.M.)
| | - Ornella Rossetto
- Department of Biomedical Sciences, University of Padova, Italy (M.P., O.R., C.M.); Neurologic Department, University-Hospital S. Maria della Misericordia, Udine, Italy (R.E.); and Consiglio Nazionale delle Ricerche, Institute of Neuroscience, University of Padova, Italy (C.M.)
| | - Roberto Eleopra
- Department of Biomedical Sciences, University of Padova, Italy (M.P., O.R., C.M.); Neurologic Department, University-Hospital S. Maria della Misericordia, Udine, Italy (R.E.); and Consiglio Nazionale delle Ricerche, Institute of Neuroscience, University of Padova, Italy (C.M.)
| | - Cesare Montecucco
- Department of Biomedical Sciences, University of Padova, Italy (M.P., O.R., C.M.); Neurologic Department, University-Hospital S. Maria della Misericordia, Udine, Italy (R.E.); and Consiglio Nazionale delle Ricerche, Institute of Neuroscience, University of Padova, Italy (C.M.)
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8
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Morineaux V, Mazuet C, Hilaire D, Enche J, Popoff MR. Characterization of botulinum neurotoxin type A subtypes by immunocapture enrichment and liquid chromatography–tandem mass spectrometry. Anal Bioanal Chem 2015; 407:5559-70. [DOI: 10.1007/s00216-015-8707-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Revised: 03/31/2015] [Accepted: 04/14/2015] [Indexed: 12/21/2022]
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9
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Popoff MR, Bouvet P. Genetic characteristics of toxigenic Clostridia and toxin gene evolution. Toxicon 2013; 75:63-89. [DOI: 10.1016/j.toxicon.2013.05.003] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Revised: 04/30/2013] [Accepted: 05/08/2013] [Indexed: 12/14/2022]
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10
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Mizanur RM, Frasca V, Swaminathan S, Bavari S, Webb R, Smith LA, Ahmed SA. The C terminus of the catalytic domain of type A botulinum neurotoxin may facilitate product release from the active site. J Biol Chem 2013; 288:24223-33. [PMID: 23779108 DOI: 10.1074/jbc.m113.451286] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Botulinum neurotoxins are the most toxic of all compounds. The toxicity is related to a poor zinc endopeptidase activity located in a 50-kDa domain known as light chain (Lc) of the toxin. The C-terminal tail of Lc is not visible in any of the currently available x-ray structures, and it has no known function but undergoes autocatalytic truncations during purification and storage. By synthesizing C-terminal peptides of various lengths, in this study, we have shown that these peptides competitively inhibit the normal catalytic activity of Lc of serotype A (LcA) and have defined the length of the mature LcA to consist of the first 444 residues. Two catalytically inactive mutants also inhibited LcA activity. Our results suggested that the C terminus of LcA might interact at or near its own active site. By using synthetic C-terminal peptides from LcB, LcC1, LcD, LcE, and LcF and their respective substrate peptides, we have shown that the inhibition of activity is specific only for LcA. Although a potent inhibitor with a Ki of 4.5 μm, the largest of our LcA C-terminal peptides stimulated LcA activity when added at near-stoichiometric concentration to three versions of LcA differing in their C-terminal lengths. The result suggested a product removal role of the LcA C terminus. This suggestion is supported by a weak but specific interaction determined by isothermal titration calorimetry between an LcA C-terminal peptide and N-terminal product from a peptide substrate of LcA. Our results also underscore the importance of using a mature LcA as an inhibitor screening target.
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Affiliation(s)
- Rahman M Mizanur
- Integrated Toxicology Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland 21702, USA
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11
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Šilhár P, Lardy MA, Hixon MS, Shoemaker CB, Barbieri JT, Struss AK, Lively JM, Javor S, Janda KD. The C-terminus of Botulinum A Protease Has Profound and Unanticipated Kinetic Consequences Upon the Catalytic Cleft. ACS Med Chem Lett 2013; 4:283-287. [PMID: 23565325 DOI: 10.1021/ml300428s] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) are among the most deadly poisons known though ironically, they also are of great therapeutic utility. A number of research programs have been initiated to discover small molecule inhibitors of BoNTs metalloprotease activity. Many, though not all of these programs have screened against a truncated and more stable form of the enzyme, that possess comparable catalytic properties to the full length enzyme. Interestingly, several classes of inhibitors notably the hydroxamates, display a large shift in potency between the two enzyme forms. In this report we compare the kinetics of active-site, alpha-exosite and beta-exosite inhibitors versus truncated and full length enzyme. Molecular dynamics simulations conducted with the truncated and homology models of the fully length BoNT LC/A indicate the flexibility of the C-terminus of the full length enzyme is responsible for the potency shifts of active-site proximally binding inhibitors while distal binding (alpha-exosite) inhibitors remain equipotent.
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Affiliation(s)
- Peter Šilhár
- Departments of Chemistry and
Immunology, and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey
Pines Road, La Jolla, California 92037, United States
| | - Matthew A. Lardy
- Takeda California Inc., 10410 Science Center Drive, San Diego, California
92121, United States
| | - Mark S. Hixon
- Takeda California Inc., 10410 Science Center Drive, San Diego, California
92121, United States
| | - Charles B. Shoemaker
- Department
of Biomedical Sciences, Tufts Cummings School of Veterinary Medicine, 200 Westboro
Road, North Grafton, Massachusetts 01536, United States
| | - Joseph T. Barbieri
- Department of Microbiology and
Molecular Genetics, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, Wisconsin 53226, United States
| | - Anjali K. Struss
- Departments of Chemistry and
Immunology, and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey
Pines Road, La Jolla, California 92037, United States
| | - Jenny M. Lively
- Departments of Chemistry and
Immunology, and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey
Pines Road, La Jolla, California 92037, United States
| | - Sacha Javor
- Departments of Chemistry and
Immunology, and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey
Pines Road, La Jolla, California 92037, United States
| | - Kim D. Janda
- Departments of Chemistry and
Immunology, and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey
Pines Road, La Jolla, California 92037, United States
- Worm Institute for Research
and Medicine (WIRM), The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, United
States
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12
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Toth S, Brueggmann EE, Oyler GA, Smith LA, Hines HB, Ahmed SA. Tyrosine phosphorylation of botulinum neurotoxin protease domains. Front Pharmacol 2012; 3:102. [PMID: 22675300 PMCID: PMC3366388 DOI: 10.3389/fphar.2012.00102] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Accepted: 05/07/2012] [Indexed: 01/17/2023] Open
Abstract
Botulinum neurotoxins are most potent of all toxins. Their N-terminal light chain domain (Lc) translocates into peripheral cholinergic neurons to exert its endoproteolytic action leading to muscle paralysis. Therapeutic development against these toxins is a major challenge due to their in vitro and in vivo structural differences. Although three-dimensional structures and reaction mechanisms are very similar, the seven serotypes designated A through G vastly vary in their intracellular catalytic stability. To investigate if protein phosphorylation could account for this difference, we employed Src-catalyzed tyrosine phosphorylation of the Lc of six serotypes namely LcA, LcB, LcC1, LcD, LcE, and LcG. Very little phosphorylation was observed with LcD and LcE but LcA, LcB, and LcG were maximally phosphorylated by Src. Phosphorylation of LcA, LcB, and LcG did not affect their secondary and tertiary structures and thermostability significantly. Phosphorylation of Y250 and Y251 made LcA resistant to autocatalysis and drastically reduced its kcat/Km for catalysis. A tyrosine residue present near the essential cysteine at the C-terminal tail of LcA, LcB, and LcG was readily phosphorylated in vitro. Inclusion of a competitive inhibitor protected Y426 of LcA from phosphorylation, shedding light on the role of the C-terminus in the enzyme’s substrate or product binding.
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Affiliation(s)
- Stephen Toth
- Integrated Toxicology Division, Department of Biochemistry and Cell Biology, United States Army Medical Research Institute of Infectious Diseases Fort Detrick, MD, USA
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13
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Light chain separated from the rest of the type a botulinum neurotoxin molecule is the most catalytically active form. PLoS One 2010; 5:e12872. [PMID: 20877571 PMCID: PMC2943925 DOI: 10.1371/journal.pone.0012872] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Accepted: 08/20/2010] [Indexed: 11/19/2022] Open
Abstract
Botulinum neurotoxins (BoNT) are the most potent of all toxins. The 50 kDa N-terminal endopeptidase catalytic light chain (LC) of BoNT is located next to its central, putative translocation domain. After binding to the peripheral neurons, the central domain of BoNT helps the LC translocate into cytosol where its proteolytic action on SNARE (soluble NSF attachment protein receptor) proteins blocks exocytosis of acetyl choline leading to muscle paralysis and eventual death. The translocation domain also contains 105 Å -long stretch of ∼100 residues, known as “belt,” that crosses over and wraps around the LC to shield the active site from solvent. It is not known if the LC gets dissociated from the rest of the molecule in the cytosol before catalysis. To investigate the structural identity of the protease, we prepared four variants of type A BoNT (BoNT/A) LC, and compared their catalytic parameters with those of BoNT/A whole toxin. The four variants were LC + translocation domain, a trypsin-nicked LC + translocation domain, LC + belt, and a free LC. Our results showed that Km for a 17-residue SNAP-25 (synaptosomal associated protein of 25 kDa) peptide for these constructs was not very different, but the turnover number (kcat) for the free LC was 6-100-fold higher than those of its four variants. Moreover, none of the four variants of the LC was prone to autocatalysis. Our results clearly demonstrated that in vitro, the LC minus the rest of the molecule is the most catalytically active form. The results may have implication as to the identity of the active, toxic moiety of BoNT/A in vivo.
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14
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Affiliation(s)
- Mauricio Montal
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, California 92093-0366;
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15
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Henkel JS, Jacobson M, Tepp W, Pier C, Johnson EA, Barbieri JT. Catalytic properties of botulinum neurotoxin subtypes A3 and A4. Biochemistry 2010; 48:2522-8. [PMID: 19256469 DOI: 10.1021/bi801686b] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Botulinum toxins (BoNT) are zinc proteases (serotypes A-G) which cause flaccid paralysis through the cleavage of SNARE proteins within motor neurons. BoNT/A was originally organized into two subtypes, BoNT/A1 and BoNT/A2, which are approximately 95% homologous and possess similar catalytic activities. Subsequently, two additional subtypes were identified, BoNT/A3 (Loch Maree) and BoNT/A4 (657Ba), which are 81 and 88% homologous with BoNT/A1, respectively. Alignment studies predicted that BoNT/A3 and BoNT/A4 were sufficiently different from BoNT/A1 to affect SNAP25 binding and cleavage. Recombinant light chain (LC) of BoNT/A3 (LC/A3) and BoNT/A4 (LC/A4) were subjected to biochemical analysis. LC/A3 cleaved SNAP25 at 50% of the rate of LC/A1 but cleaved SNAPtide at a faster rate than LC/A1, while LC/A4 cleaved SNAP25 and SNAPtide at slower rates than LC/A1. LC/A3 and LC/A4 had similar K(m) values for SNAP25 relative to LC/A1, while the k(cat) for LC/A4 was 10-fold slower than that for LC/A1, suggesting a defect in substrate cleavage. Neither LC/A3 nor LC/A4 possessed autocatalytic activity, a property of LC/A1 and LC/A2. Thus, the four subtypes of BoNT/A bind SNAP25 with similar affinity but have different catalytic capacities for SNAP25 cleavage, SNAPtide cleavage, and autocatalysis. The catalytic properties identified among the subtypes of LC/A may influence strategies for the development of small molecule or peptide inhibitors as therapies against botulism.
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Affiliation(s)
- James S Henkel
- Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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16
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Toth SI, Smith LA, Ahmed SA. Extreme sensitivity of botulinum neurotoxin domains towards mild agitation. J Pharm Sci 2009; 98:3302-11. [PMID: 19226630 DOI: 10.1002/jps.21676] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Botulinum neurotoxins (BoNTs) and their fragments are targets of therapeutic developments and are increasingly used as therapeutic, prophylactic, and research reagents. However, published data on their properties vary widely. In order to gain a better understanding of these variations, we initiated a systematic investigation of the stability parameters of catalytic light chains (Lc) as well as of cell surface binding domains (Hc) of the neurotoxin. When followed by CD spectroscopy, we noticed that the recombinant light chains of serotypes A (LcA), B, D, E, and G rapidly lost their secondary structures by mild stirring. Denaturation of LcA increased with stirring speed and temperature resulting in a catalytically inactive precipitate. Reducing agents or an anaerobic environment were ineffective in the denaturation. Under identical conditions, bovine serum albumin, ovalbumin, carboxypeptidase B, and of thermolysin, a structural and functional analogue of LcA, remained unchanged. Hc domains of serotype A, B, C, E, and F were also denatured by mild stirring. Adding the nonionic detergent Tween-20 to LcA completely prevented the denaturation. We speculate that the BoNT domains undergo surface denaturation due to rapid exposure of hydrophobic residues by mechanical agitation. This study has important implications for handling BoNT proteins used in therapeutic development.
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Affiliation(s)
- Stephen I Toth
- Department Molecular Biology, Integrated Toxicology Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland 21702, USA
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17
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Identification of residues surrounding the active site of type A botulinum neurotoxin important for substrate recognition and catalytic activity. Protein J 2008; 27:151-62. [PMID: 18213512 DOI: 10.1007/s10930-007-9118-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Type A botulinum neurotoxin is one of the most lethal of the seven serotypes and is increasingly used as a therapeutic agent in neuromuscular dysfunctions. Its toxic function is related to zinc-endopeptidase activity of the N-terminal light chain (LC) on synaptosome-associated protein-25 kDa (SNAP-25) of the SNARE complex. To understand the determinants of substrate specificity and assist the development of strategies for effective inhibitors, we used site-directed mutagenesis to investigate the effects of 13 polar residues of the LC on substrate binding and catalysis. Selection of the residues for mutation was based on a computational analysis of the three-dimensional structure of the LC modeled with a 17-residue substrate fragment of SNAP-25. Steady-state kinetic parameters for proteolysis of the substrate fragment were determined for a set of 16 single mutants. Of the mutated residues non-conserved among the serotypes, replacement of Arg-230 and Asp-369 by polar or apolar residues resulted in drastic lowering of the catalytic rate constant (k(ca)), but had less effect on substrate affinity (K(m)). Substitution of Arg-230 with Lys decreased the catalytic efficiency (k(cat)/K(m)) by 50-fold, whereas replacement by Leu yielded an inactive protein. Removal of the electrostatic charge at Asp-369 by mutation to Asn resulted in 140-fold decrease in k(cat)/K(m). Replacement of other variable residues surrounding the catalytic cleft (Glu-54, Glu-63, Asn-66, Asp-130, Asn-161, Glu-163, Glu-170, Glu-256), had only marginal effect on decreasing the catalytic efficiency, but unexpectedly the substitution of Lys-165 with Leu resulted in fourfold increase in k(cat)/K(m). For comparison purposes, two conserved residues Arg-362 and Tyr-365 were investigated with substitutions of Leu and Phe, respectively, and their catalytic efficiency decreased 140- and 10-fold, respectively, whereas substitution of the tyrosine ring with Asn abolished activity. The altered catalytic efficiencies of the mutants were not due to any significant changes in secondary or tertiary structures, or in zinc content and thermal stability. We suggest that, despite the large minimal substrate size for catalysis, only a few non-conserved residues surrounding the active site are important to render the LC competent for catalysis or provide conformational selection of the substrate.
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18
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Bagramyan K, Barash JR, Arnon SS, Kalkum M. Attomolar detection of botulinum toxin type A in complex biological matrices. PLoS One 2008; 3:e2041. [PMID: 18446228 PMCID: PMC2323579 DOI: 10.1371/journal.pone.0002041] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2008] [Accepted: 03/15/2008] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND A highly sensitive, rapid and cost efficient method that can detect active botulinum neurotoxin (BoNT) in complex biological samples such as foods or serum is desired in order to 1) counter the potential bioterrorist threat 2) enhance food safety 3) enable future pharmacokinetic studies in medical applications that utilize BoNTs. METHODOLOGY/PRINCIPAL FINDINGS Here we describe a botulinum neurotoxin serotype A assay with a large immuno-sorbent surface area (BoNT/A ALISSA) that captures a low number of toxin molecules and measures their intrinsic metalloprotease activity with a fluorogenic substrate. In direct comparison with the "gold standard" mouse bioassay, the ALISSA is four to five orders of magnitudes more sensitive and considerably faster. Our method reaches attomolar sensitivities in serum, milk, carrot juice, and in the diluent fluid used in the mouse assay. ALISSA has high specificity for the targeted type A toxin when tested against alternative proteases including other BoNT serotypes and trypsin, and it detects the holotoxin as well as the multi-protein complex form of BoNT/A. The assay was optimized for temperature, substrate concentration, size and volume proportions of the immuno-sorbent matrix, enrichment and reaction times. Finally, a kinetic model is presented that is consistent with the observed improvement in sensitivity. CONCLUSIONS/SIGNIFICANCE The sensitivity, specificity, speed and simplicity of the BoNT ALISSA should make this method attractive for diagnostic, biodefense and pharmacological applications.
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Affiliation(s)
- Karine Bagramyan
- Immunology Division, Beckman Research Institute of the City of Hope, Duarte, California, United States of America
| | - Jason R. Barash
- Infant Botulism Treatment and Prevention Program, California Department of Public Health, Richmond, California, United States of America
| | - Stephen S. Arnon
- Infant Botulism Treatment and Prevention Program, California Department of Public Health, Richmond, California, United States of America
| | - Markus Kalkum
- Immunology Division, Beckman Research Institute of the City of Hope, Duarte, California, United States of America
- * E-mail:
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19
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Brunger AT, Breidenbach MA, Jin R, Fischer A, Santos JS, Montal M. Botulinum neurotoxin heavy chain belt as an intramolecular chaperone for the light chain. PLoS Pathog 2007; 3:1191-4. [PMID: 17907800 PMCID: PMC1994969 DOI: 10.1371/journal.ppat.0030113] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Axel T Brunger
- * To whom correspondence should be addressed. E-mail: (ATB), (MM)
| | | | | | | | | | - Mauricio Montal
- * To whom correspondence should be addressed. E-mail: (ATB), (MM)
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20
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Chen X, Deng Y. Long-time molecular dynamics simulations of botulinum biotoxin type-A at different pH values and temperatures. J Mol Model 2007; 13:559-72. [PMID: 17333307 DOI: 10.1007/s00894-007-0178-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2006] [Accepted: 01/26/2007] [Indexed: 10/23/2022]
Abstract
Botulinum neurotoxins type A (BoNT/A) are highly potent toxins, but are also useful in the treatment of illnesses. We studied the properties of BoNT/A at various temperatures and pH values in order to understand its toxicity and structure variations. The pH values of the environment of BoNT/A are obtained by changing the protonation states of certain titratable residue groups. Our results show that certain parts of the protein are active at acidic pH environments or at high temperatures. The protein is more stable in neutral environments at normal human body temperature, whereas, at high temperature, the protein is more stable in acidic environments. Also, the three domains of the protein tend to have relative motion rather than within individual domains.
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Affiliation(s)
- Xin Chen
- Department of Physics, Stony Brook University, Stony Brook, NY 11794, USA.
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21
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Chen S, Kim JJP, Barbieri JT. Mechanism of substrate recognition by botulinum neurotoxin serotype A. J Biol Chem 2007; 282:9621-9627. [PMID: 17244603 DOI: 10.1074/jbc.m611211200] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Botulinum neurotoxins (BoNTs) are zinc proteases that cleave SNARE proteins to elicit flaccid paralysis by inhibiting neurotransmitter-carrying vesicle fusion to the plasma membrane of peripheral neurons. Unlike other zinc proteases, BoNTs recognize extended regions of SNAP25 for cleavage; however, the molecular basis for this extended substrate recognition is unclear. Here, we define a multistep mechanism for recognition and cleavage of SNAP25 by BoNT/A. SNAP25 initially binds along the belt region of BoNT/A, which aligns the P5 residue to the S5 pocket at the periphery of the active site. Although the exact order of each step of recognition of SNAP25 by BoNT/A at the active site is not clear, the initial binding could subsequently orient the P4'-residue of SNAP25 to form a salt bridge with the S4'-residue, which opens the active site allowing the P1'-residue access to the S1'-pocket. Subsequent hydrophobic interactions between the P3 residue of SNAP25 and the S3 pocket optimize alignment of the scissile bond for cleavage. This explains how the BoNTs recognize and cleave specific coiled SNARE substrates and provides insight into the development of inhibitors to prevent botulism.
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Affiliation(s)
- Sheng Chen
- Departments of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Jung-Ja P Kim
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Joseph T Barbieri
- Departments of Microbiology and Molecular Genetics, Medical College of Wisconsin, Milwaukee, Wisconsin 53226.
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22
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DasGupta BR. Botulinum neurotoxins: perspective on their existence and as polyproteins harboring viral proteases. J GEN APPL MICROBIOL 2006; 52:1-8. [PMID: 16598153 DOI: 10.2323/jgam.52.1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Bibhuti R DasGupta
- Department of Food Microbiology and Toxicology, University of Wisconsin-Madison, 53706, USA.
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23
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Dasgupta BR, Antharavally BS, Tepp W, Evenson ML. Botulinum neurotoxin types A, B, and E: fragmentations by autoproteolysis and other mechanisms including by O-phenanthroline-dithiothreitol, and association of the dinucleotides NAD(+)/NADH with the heavy chain of the three neurotoxins. Protein J 2006; 24:337-68. [PMID: 16323041 DOI: 10.1007/s10930-005-7589-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2005] [Indexed: 10/25/2022]
Abstract
The first evidence of autoproteolytic activity of the approximately 50-kDa light chain of the clostridial neurotoxins (NT) is traceable to the observations that the light chains of botulinum NT serotypes A and E, separated from their approximately 100-kDa heavy chain conjugate, were found cleaved at the amino side of Tyr250 and Arg244, respectively [DasGupta and Foley (1989). Biochimie 71: 1183-1200]. Specific cleavages of the recombinant light chain of NT type A, including at Tyr249-Tyr250, firmly established that the cleavages reported earlier were due to autoproteolysis [Ahmed et al. (2001). J. Protein Chem. 20: 221-231; Ahmed et al. (2003). Biochemistry 42:12539-12549] and not by contaminating proteases or non-enzymatic. We now report many cleavages in the NT types A, B and E and also in their separated light and heavy chains, and identification of several of the peptide bonds cleaved. None of the identified cleaved bonds (-P1-P1' -) in one serotype (except Asp-Pro) was found common in other serotypes or cleaved within itself at a second site. After separation from the heavy chain self-cleavages of the light chains of type A, B and E at Tyr249-Tyr250, Gln258-Ser259 and Ile243-Arg244, respectively indicate an intriguing feature (in the aligned sequences these bonds of type A and B are 2 and type A and E are 4 peptide bonds apart) that may have some role in the NT's structure-function relationship yet to be understood. We point out that autoproteolysis of a single peptide bond (Phe418-Thr419 or Phe422-Glu423) in NT type A reported by Ahmed et al. (2001) can potentially generate proteolytically active light chain freed of the heavy chain; this is an efficient pathway, that by-passes nicking by a trypsin-like protease(s) inside the intrachain disulfide bridge and its reductive cleavage. We offer probable explanations for the observed cleavages such as acid- and metal-mediated (non-catalytic and non-stoichiometric) reactions in addition to autoproteolysis but cannot predict which mechanism(s) of cleavage occur or prevail following NT's entry in the body as poison or therapeutic agent. The metal chelator O-phenanthroline (above critical miceller concentration) in the presence of dithiothreitol cleaved type E NT at limited sites generating discrete 114-, 87-, 49-, 42-, and 31-kDa fragments but degraded NTs type A and B extensively. The limited cleavage of type E NT was dependent on the presence of metal ion(s) bound to the protein and its native (urea sensitive) conformation. The self-cleavage of the NTs at specific sites prompted us to search for specific binding sites on the NTs analogous to SNARE-motifs-the 9-residuelong motifs present on the NT's natural substrates (SNAP-25, syntaxin, VAMP/synaptobrevin); such putative binding motifs (sites) noted on all clostridial NTs are reported here. Their relationship to the observed autoproteolysis remains to be determined experimentally. The dinucleotide NAD(+)/NADH associated with the NTs type A, B and E (2-3 NADH per protein molecule) via their H-chains, and a portion of the H-chain (toward the C-terminus) appears to exhibit limited amino acid sequence homology with lactate dehydrogenase-a representative NAD(+)/NADH binding protein.
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Affiliation(s)
- Bibhuti R Dasgupta
- Department of Food Microbiology and Toxicology, University of Wisconsin - Madison, 1925 Willow Drive, Madison, WI 53706, USA.
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24
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Gilsdorf J, Gul N, Smith LA. Expression, purification, and characterization of Clostridium botulinum type B light chain. Protein Expr Purif 2005; 46:256-67. [PMID: 16297638 DOI: 10.1016/j.pep.2005.09.024] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2005] [Revised: 09/13/2005] [Accepted: 09/17/2005] [Indexed: 10/25/2022]
Abstract
A full-length synthetic gene encoding the light chain of botulinum neurotoxin serotype B, approximately 50 kDa (BoNT/B LC), has been cloned into a bacterial expression vector pET24a+. BoNT/B LC was expressed in Escherichia coli BL21.DE3.pLysS and isolated from the soluble fraction. The resultant protein was purified to homogeneity by cation chromatography and was determined to be >98% pure as assessed by SDS-polyacrylamide gel stained with SilverXpress and analyzed by densitometry. Mass spectroscopic analysis indicated the protein to be 50.8 kDa, which equaled the theoretically expected mass. N-terminal sequencing of the purified protein showed the sequence corresponded to the known reported sequence. The recombinant BoNT/B light chain was found to be highly stable, catalytically active, and has been used to prepare antisera that neutralizes against BoNT/B challenge. Characterization of the protein including pH, temperature, and the stability of the protein in the presence or absence of zinc is described within. The influence of pH differences, buffer, and added zinc on secondary and tertiary structure of BoNT/B light chain was analyzed by circular dichroism and tryptophan fluorescence measurements. Optimal conditions for obtaining maximum metalloprotease activity and stabilizing the protein for long term storage were determined. We further analyzed the thermal denaturation of BoNT/B LC as a function of temperature to probe the pH and added zinc effects on light chain stability. The synthetic BoNT/B LC has been found to be highly active on its substrate (vesicle associated membrane protein-2) and, therefore, can serve as a useful reagent for BoNT/B research.
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Affiliation(s)
- Janice Gilsdorf
- Integrated Toxicology Division, U.S. Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Frederick, MD 21702-5011, USA
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25
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Burnett JC, Schmidt JJ, McGrath CF, Nguyen TL, Hermone AR, Panchal RG, Vennerstrom JL, Kodukula K, Zaharevitz DW, Gussio R, Bavari S. Conformational sampling of the botulinum neurotoxin serotype a light chain: implications for inhibitor binding. Bioorg Med Chem 2005; 13:333-41. [PMID: 15598556 DOI: 10.1016/j.bmc.2004.10.026] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2004] [Revised: 10/09/2004] [Accepted: 10/09/2004] [Indexed: 10/26/2022]
Abstract
Botulinum neurotoxins (BoNTs) are the most potent of the known biological toxins, and consequently are listed as category A biowarfare agents. Currently, the only treatments against BoNTs include preventative antitoxins and long-term supportive care. Consequently, there is an urgent need for therapeutics to counter these enzymes--post exposure. In a previous study, we identified a number of small, nonpeptidic lead inhibitors of BoNT serotype A light chain (BoNT/A LC) metalloprotease activity, and we identified a common pharmacophore for these molecules. In this study, we have focused on how the dynamic movement of amino acid residues in and surrounding the substrate binding cleft of the BoNT/A LC might affect inhibitor binding modes. The X-ray crystal structures of two BoNT/A LCs (PDB refcodes=3BTA and 1E1H) were examined. Results from these analyses indicate that the core structural features of the examined BoNT/A LCs, including alpha-helices and beta-sheets, remained relatively unchanged during 1 ns dynamics trajectories. However, conformational flexibility was observed in surface loops bordering the substrate binding clefts in both examined structures. Our analyses indicate that these loops may possess the ability to decrease the solvent accessibility of the substrate binding cleft, while at the same time creating new residue contacts for the inhibitors. Loop movements and conformational/positional analyses of residues within the substrate binding cleft are discussed with respect to BoNT/A LC inhibitor binding and our common pharmacophore for inhibition. The results from these studies may aid in the future identification/development of more potent small molecule inhibitors that take advantage of new binding contacts in the BoNT/A LC.
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Affiliation(s)
- James C Burnett
- Developmental Therapeutics Program, NCI Frederick, Frederick, MD 21702, USA
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26
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Segelke B, Knapp M, Kadkhodayan S, Balhorn R, Rupp B. Crystal structure of Clostridium botulinum neurotoxin protease in a product-bound state: Evidence for noncanonical zinc protease activity. Proc Natl Acad Sci U S A 2004; 101:6888-93. [PMID: 15107500 PMCID: PMC406437 DOI: 10.1073/pnas.0400584101] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Clostridium botulinum neurotoxins (BoNTs), the most potent toxins known, disrupt neurotransmission through proteolysis of proteins involved in neuroexocytosis. The light chains of BoNTs are unique zinc proteases that have stringent substrate specificity and require exceptionally long substrates. We have determined the crystal structure of the protease domain from BoNT serotype A (BoNT/A). The structure reveals a homodimer in a product-bound state, with loop F242-V257 from each monomer deeply buried in its partner's catalytic site. The loop, which acts as a substrate, is oriented in reverse of the canonical direction for other zinc proteases. The Y249-Y250 peptide bond of the substrate loop is hydrolyzed, leaving the Y249 product carboxylate coordinated to the catalytic zinc. From the crystal structure of the BoNT/A protease, detailed models of noncanonical binding and proteolysis can be derived which we propose are also consistent with BoNT/A binding and proteolysis of natural substrate synaptosome-associated protein of 25 kDa (SNAP-25). The proposed BoNT/A substrate-binding mode and catalytic mechanism are markedly different from those previously proposed for the BoNT serotype B.
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Affiliation(s)
- Brent Segelke
- University of California, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94551, USA
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27
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Graille M, Mora L, Buckingham RH, van Tilbeurgh H, de Zamaroczy M. Structural inhibition of the colicin D tRNase by the tRNA-mimicking immunity protein. EMBO J 2004; 23:1474-82. [PMID: 15014439 PMCID: PMC391069 DOI: 10.1038/sj.emboj.7600162] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2004] [Accepted: 02/13/2004] [Indexed: 11/09/2022] Open
Abstract
Colicins are toxins secreted by Escherichia coli in order to kill their competitors. Colicin D is a 75 kDa protein that consists of a translocation domain, a receptor-binding domain and a cytotoxic domain, which specifically cleaves the anticodon loop of all four tRNA(Arg) isoacceptors, thereby inactivating protein synthesis and leading to cell death. Here we report the 2.0 A resolution crystal structure of the complex between the toxic domain and its immunity protein ImmD. Neither component shows structural homology to known RNases or their inhibitors. In contrast to other characterized colicin nuclease-Imm complexes, the colicin D active site pocket is completely blocked by ImmD, which, by bringing a negatively charged cluster in opposition to a positively charged cluster on the surface of colicin D, appears to mimic the tRNA substrate backbone. Site-directed mutations affecting either the catalytic domain or the ImmD protein have led to the identification of the residues vital for catalytic activity and for the tight colicin D/ImmD interaction that inhibits colicin D toxicity and tRNase catalytic activity.
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Affiliation(s)
| | | | | | - Herman van Tilbeurgh
- LEBS, CNRS, UPR 9063, Gif sur Yvette, France
- IBBMC, CNRS, UMR 8619, Université Paris 11, Orsay, France
| | - Miklos de Zamaroczy
- IBPC, CNRS, UPR 9073, Paris, France
- IBPC, CNRS, UPR 9073, 13 rue Pierre et Marie Curie, 75005 Paris, France. Tel.: +33 1 5841 51 54; Fax: +33 1 5841 50 20; E-mail:
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28
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Smith LA, Jensen MJ, Montgomery VA, Brown DR, Ahmed SA, Smith TJ. Roads from vaccines to therapies. Mov Disord 2004; 19 Suppl 8:S48-52. [PMID: 15027054 DOI: 10.1002/mds.20009] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Over the past decade, we have demonstrated that various recombinant fragments of botulinum neurotoxin are highly immunogenic, stimulating notable levels of protective antibodies in mice, guinea pigs, and nonhuman primates. One of the fragments evaluated, the fragment C, is a potential next-generation vaccine candidate to replace the current pentavalent botulinum toxoid vaccine. Synthetic genes encoding the carboxyl-terminal regions (approximately 50 kDa) of toxin types A, B, C1, E, and F were expressed in Pichia pastoris, and manufacturing processes were developed for producing highly purified vaccines. These vaccines were shown to be safe, highly efficacious, stable, and amenable to high-level industrial production. Recombinant vaccines are now being produced in accordance with current Good Manufacturing Practices for use in future clinical trials. As our discovery-based program on vaccine development is diminishing, it is concurrently being replaced with a program focused on developing therapeutic interventions to botulism. Synthetic genes encoding the light chains of botulinum toxin have been expressed in Escherichia coli, and purified. These proteolytically active light chains are being used in high-throughput assays to screen for inhibitors of its catalytic activity. Other resources developed as part of the vaccine initiative, likewise, are finding utility in the quest to develop therapies for botulism.
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Affiliation(s)
- Leonard A Smith
- Division of Toxinology and Aerobiology, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland 21702-5011, USA.
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29
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Jensen MJ, Smith TJ, Ahmed SA, Smith LA. Expression, purification, and efficacy of the type A botulinum neurotoxin catalytic domain fused to two translocation domain variants. Toxicon 2003; 41:691-701. [PMID: 12727273 DOI: 10.1016/s0041-0101(03)00042-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Clostridial neurotoxins are potent inhibitors of synaptic function, with the zinc-dependent proteolytic light chain (LC) portion of the toxin cleaving one of three neural SNARE proteins. In nature, the LC is expressed as a part of a much larger toxin and hemagglutinin complex, protecting it from environmental degradation and preserving its catalytic activity. We developed forms of the LC of type A botulinum neurotoxin (BoNT-A) with parts of the larger toxin gene, for use as reagents in high-throughput assays to screen for potential LC antagonists, to further elucidate the toxin's mechanism of action, and to study immunological responses to the toxin. Three BoNT-A constructs were engineered and expressed: the LC, LC with translocation region (LC+H(n)), and the LC with the belt portion of the translocation region (LC+Belt). Purification was optimized to a two-step process, with relatively high yields of all three constructs obtained. Activity assays showed all three constructs to be active, with the LC being the most active. Immunogenic protection against native BoNT-A toxin challenge was observed for all three constructs, with the best protection observed with the LC+H(n) and LC+Belt proteins.
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Affiliation(s)
- M J Jensen
- Division of Toxinology and Aerobiology, United States Army Medical Research Institute of Infectious Diseases, 1425 Porter Street, Fort Detrick, MD 21702-5011, USA
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Schmidt JJ, Stafford RG. Fluorigenic substrates for the protease activities of botulinum neurotoxins, serotypes A, B, and F. Appl Environ Microbiol 2003; 69:297-303. [PMID: 12514008 PMCID: PMC152407 DOI: 10.1128/aem.69.1.297-303.2003] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The seven botulinum neurotoxins (BoNTs) are zinc metalloproteases that cleave neuronal proteins involved in neurotransmitter release and are among the most toxic natural products known. High-throughput BoNT assays are needed for use in antibotulinum drug discovery and to characterize BoNT protease activities. Compared to other proteases, BoNTs exhibit unusually stringent substrate requirements with respect to amino acid sequences and polypeptide lengths. Nonetheless, we have devised a strategy for development of fluorigenic BoNT protease assays, based on earlier structure-function studies, that has proven successful for three of the seven serotypes: A, B, and F. In synthetic peptide substrates, the P(1) and P(3)' residues were substituted with 2,4-dinitrophenyl-lysine and S-(N-[4-methyl-7-dimethylamino-coumarin-3-yl]-carboxamidomethyl)-cysteine, respectively. By monitoring the BoNT-catalyzed increase in fluorescence over time, initial hydrolysis rates could be obtained in 1 to 2 min when BoNT concentrations were 60 ng/ml (about 1 nM) or higher. Each BoNT cleaved its fluorigenic substrate at the same location as in the neuronal target protein, and kinetic constants indicated that the substrates were selective and efficient. The fluorigenic assay for BoNT B was used to characterize a new competitive inhibitor of BoNT B protease activity with a K(i) value of 4 micro M. In addition to real-time activity measurements, toxin concentration determinations, and kinetic studies, the BoNT substrates described herein may be directly incorporated into automated high-throughput assay systems to screen large numbers of compounds for potential antibotulinum drugs.
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Affiliation(s)
- James J Schmidt
- Toxinology and Aerobiology Division, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, Maryland 21702-5011, USA.
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Sagane Y, Watanabe T, Kouguchi H, Sunagawa H, Obata S, Oguma K, Ohyama T. Spontaneous nicking in the nontoxic-nonhemagglutinin component of the Clostridium botulinum toxin complex. Biochem Biophys Res Commun 2002; 292:434-40. [PMID: 11906181 DOI: 10.1006/bbrc.2002.6689] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The nontoxic-nonhemagglutinin (NTNHA) component, in both isolated form and the neurotoxin (NT)/NTNHA complexed form, was prepared protease-free from toxin complexes produced by Clostridium botulinum type D strain 4947. NTNHA in both preparations was found to be spontaneously converted to the nicked NTNHA form leading to 15- and 115-kDa fragments with the excision of several amino acid residues at specific sites on SDS-PAGE during long-term incubation, while that of the NT/NTNHA/hemagglutinin complexed form remained unnicked single-chain polypeptides under the same conditions. Considering that the NTNHA preparation contained small amounts of the nicked form of NTNHA and the addition of trypsin accelerated the cleavage, it is speculated that a nicked form of NTNHA remaining after the purification and/or NTNHA itself catalyzes the cleavage of intact NTNHA.
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Affiliation(s)
- Yoshimasa Sagane
- Department of Food Science and Technology, Faculty of Bioindustry, Tokyo University of Agriculture, 196 Yasaka, Abashiri 099-2493, Japan
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